The Status of Data Recovery - A Growing Need For Today's Businesses

For almost as long as people have been putting digital data on magnetic media, their precious information has been getting lost. In the good old days, perhaps 20 years ago, any company or institution that lost its data was on its own. Anyone with the expertise to help was probably already either on staff or employed by the equipment vendor.

Things started to change with the growth and development of the Information Technology industry, on both the hardware and software sides. As systems multiplied and became more complex, so did the various misfortunes that could beset an organization's data.

Enter the data recovery specialist. About 15 years ago, the first outside consultants began to get frantic calls from clients to come in and rescue their information. At that time, much of the expertise was based on proprietary software tools, written to perform on hardware from specific vendors. It took some years before companies began to specialize in data recovery. Because many data loss situations call for a 'physical', hardware solution, the larger companies made the major investments necessary to offer 'clean rooms' - laboratories where malfunctioning or damaged disk drives can be disassembled or reconfigured to yield whatever data remains.

Today, the industry is crisis-driven. Depending on how well sprinkler systems or disk drive designers have done their jobs, we work or rest idle.

All the tools and techniques that any data recovery company has amassed over time have developed or acquired on an 'as-needed' basis. The range of possible challenges is so broad, and the IT industry releases new products so frequently, that it would be impossible to anticipate problems before they actually occur.

Perhaps a testament to the efficiency and reliability of the latest hardware and software today, the data recovery industry is not a large one. Worldwide, there are probably 20 companies with the staff and the facilities to tackle those data-loss situations that simply cannot be resolved in-house with commercially available software or with assistance from vendors.

We have seen some companies in the data recovery field to move away from the 'physical' side of the business, specializing in software-only solutions rather than grappling hands-on with the disk drives and magnetic media to recover data. On the other hand, companies cannot specialize completely in the hardware side, because there will always be a need to adapt or write software to help harvest the data.

What about the future of the industry? Ironically, in a world that is becoming increasingly globalized, we think the successful data recovery business will have an important local dimension. Even though we can, and do reach around the world electronically to recover data, we believe customers will still place a premium on dealing with someone in their own region.

With almost 200 million disk drives shipping this year, and the risks they face out in the real world, we can confidently predict that the future holds unlimited challenge for the data recovery industry.

The Science Behind Data Recovery

The computer data that seems solid and reliable when you see it on a monitor or hard copy printout really exists only as minute electrical impulses crammed tightly on tape, diskettes or hard drives. Depending on how it is stored, that data will continue to exist until the medium is destroyed, scrambled by a virus or overwritten by other information. In other words, some 'physical' event prevents you from accessing your data. Data recovery companies work to reverse that process, any way they can.

There is no single method to retrieve data. In fact, it is extremely rare to apply a solution more than once. To avoid damage from repeated scanning, a skilled data recovery company will find a way to duplicate client data, even if it must be done bit by bit.

Hard disk drives store data store data on metal oxide platters spinning as fast as 10,000 revolutions a minute while an actuator arm reads and writes magnetic charges one millionth of an inch above the surface. Even though any contact can and does destroy data, a great deal of information can still be harvested from physically damaged media. Because the manufacturers of storage media like hard drives are constantly striving to compress more data on to smaller surfaces, a data recovery specialist must have a 'clean room' to avoid dust or dirt causing more damage to the delicate magnetic media.

Data recovery requires not only specialized equipment but people with advanced skills and the creativity to apply them in unique and demanding situations.

The Human Side of Data Loss: The Reality Of A Hard Drive Crash

Data loss is an expensive reality. It's a hard fact that it happens more often then users like to admit. A recent study by the accounting firm McGladrey and Pullen estimates that one out of every 500 data centers will experience a severe computer disaster this year. As a result, almost half of those companies will go out of business. At the very least, a data loss disaster can mean lost income and missed business opportunities.

The other side of data loss is the psychological and emotional turmoil it can cause to IT managers and business owners. Despair, panic, and the knowledge that the whole organization might be at risk are involved. In a sense, that's only fair, since human error is one of the two largest contributing factors in data loss. Together with mechanical failure, it accounts for almost 75 per cent of all incidents. (Software corruption, computer viruses and physical disasters such as fire and water damage make up the rest.)

Disk drives today are typically reliable. Human beings, it turns out, are not. A Strategic Research Corp. study done in 2000 found that approximately 15 per cent of all unplanned downtime occurred due to human error. A significant proportion of that happened because users failed to implement adequate backup procedures, either having trouble with their backups, or having no backup at all.

How does it happen that skilled, high-level users put their systems - and their businesses - at such risk?

In many cases, the problem starts long before the precipitating system error is made, that is, when users place their faith in out-of-box solutions that may not, in fact, fit their organization's needs. Instead of assessing their business and technology requirements, then going to an appropriate engineered solution, even experienced IT professionals at large corporations will often simply buy what they're sold. In this case, faith in technology can be an vice instead of a virtue.

But human intervention itself can sometimes be the straw that breaks the technology's back. When the office of a Venezuelan civil engineering firm was devastated by floods, its owners sent 17 soaked, mud-coated disks from three RAID arrays to us in plastic bags. A tough enough salvage job was made even more complex by the fact that someone had frozen the drives before shipping them. As the disks thawed, yet more damage was done. (After eight weeks of painstaking directory-by-directory recovery, all the data from the remaining fifteen disks was retrieved.)

Sometimes, the underlying cause of a data loss event is simply shoddy housekeeping. The more arduous the required backup routine, the less likely it will be done on a regular basis. A state ambulance monitoring system suffered a serious disk failure, only to discover that its automated backup hadn't run for fourteen months. A tape had jammed in the drive, but no-one had noticed.

When disaster strikes, the normal human reaction is panic. Because the loss of data signifies critical consequences, even the most competent IT staff can jump to conclusions, and take inappropriate action. A blank screen at a critical time can lead to a series of naive decisions, each one compounding the preceding error. Wrong buttons get pushed, and the disaster only gets worse. Sometimes the pressure to correct the system failure speedily can result in an attempt to reconfigure an entire RAID array. IT specialists are typically not equipped to deal with crisis modes or data recovery techniques. Just as a good physician is trained to prolong life, the skilled IT specialist is trained to keep the system running. When a patient dies, the physician turns to others, such as nurses or counselors to manage the situation. When significant data loss occurs, the IT specialist turns to the data recovery professional.

Data recovery specialists are innovative problem solvers. Often, the application of basic common sense, when no-one else is in any condition to apply it, is the beginning of the journey towards data recovery. The data recovery specialist draws on a wealth of experience, married to a "never say die" attitude, and a comprehensive tool kit of problem-solving procedures. Successful recovery outcomes hinge on a combination of innovative logistics, applied problem-solving, and "technology triage," the process of stabilizing an affected system quickly, analyzing and treating its wounds, and preparing it for surgery. The triage process sets priorities, such as targeting which files are needed first or which are absolutely vital to the functioning of the business, and establishes whether files might be recovered in less structured formats (such as text-only), which may be desirable when time is crucial.

The art and science of professional data recovery can spell the difference between a business' success or its failure. Before that level of intervention is required, though, users can take steps to ensure that the probability of a data loss disaster is minimized.

Basic to any business technology plan is a regular fire-drill procedure. Back-up routines may be in place, staff may assigned to specific roles, hardware and software may be configured - but, if the user isn't completely sure that everything works the way it should, a data loss event is inevitable. Having adequate, tested, and current backups in place is critical. A hardware breakdown should not be compounded by human error - if the malfunctioning drive is critical, the task of dealing with it should go to a data recovery professional.

Just as data loss disasters are rooted in a combination of mechanical failure and human error, so, too, the data recovery solution lies in a creative marriage of the technological and the human. The underlying philosophy of successful data recovery is that technology is something to be used by human beings, not something that uses us.

The Costs Of A Data Loss Disaster

Computer data is the life's blood of the modern organization. Losing a little means discomfort and weakness. Losing too much is death.

When a catastrophic failure hits a company's data, the costs begin mounting immediately. Employees who should be busy are idle while the work piles up. Products aren't shipped, payments aren't processed and salespeople dealing with customers are suddenly tongue-tied and stuck for answers.

Those costs are relatively easy to quantify, once the company is back in business and managers are being called to account for their actions - just multiply down-time by hourly rates, and tally up how much money was paid out in interest on late payments, and calculate how many sales were lost. The real costs of data loss are sobering. When a company suffers a computer outage longer than 10 days, there is a fifty-per cent chance it will no longer exist in five years. Most that do survive never fully recover.

Disaster strikes two out of 1,000 company data centers each year, according to one accounting firm with 43 per cent of those companies closing immediately, and another 29 per cent gone within two years.

Like hack attacks and employee sabotage, reliable information about data disasters can be hard to collect. It is probably impossible to quantify the exact dollar costs of data loss. But the personal reality of data loss is much worse than many management personnel can imagine. We are no longer surprised to have clients tell us, "It doesn't matter what it costs, just get my data back." We hear it once a week.

It gets worse. We have received media for recovery from an IT administrator one day only to learn the next day that the person had been terminated and someone else appointed in their place. The day after, when we called the company, we learned that the new person had been fired and replaced.

While it is unusual for companies to tear themselves apart during a data loss crisis, an episode can erode an organization's self-confidence. The internal damage caused by even a minor data loss can reverberate throughout the company. Line departments, feeling betrayed by IT may never again rely on company-wide systems, even if they are an appropriate response to the disaster. The IT department may well insist on strategies that centralize information resources under its control, at the expense of innovation.

Meanwhile, even the tightest security may not be able to prevent news of a data disaster spreading outside the organization. Customers, accustomed to just-in-time service and instant access to information, may find other vendors whom they perceive as more reliable. Financial organizations will look twice at any business that fails to protect its data so access to credit or capital may be cut off.

Successful data recovery companies can literally bring their clients back to life, by stopping the bleeding, restoring order from chaos and getting people back to work. Most data can be recovered quickly, most of the time. But almost all data loss incidents can be prevented, through simple, manageable, measurable policies and procedures.

Tape Cartridges and Glossary Of Tape Related Computer Terms

Access storage:

Storage conditions at or near room ambient conditions that allow tape collections to be readily accessed for immediate playback.

AES:

Abbreviation for Audio Engineering Society.

Analog recording:

A recording in which continuous magnetic signals are written to the tape that are representations of the voltage signals coming from the recording microphone or the video camera.

Analog-to-digital:

The process in which a continuous analog signal is quantized and converted to a series of binary integers.

ANSI:

Abbreviation for American National Standards Institute.

Archival storage:

Storage conditions specifically designed to extend or maximize the lifetime of stored media. Generally involves the use of temperatures and humidities lower that access storage conditions. Temperatures and humidities are also tightly controlled within a narrow range, and access by personnel is limited.

Backing:

See substrate.

Binary number:

A number that can be represented using only two numeric symbols - 0 and 1. A number in base 2.

Decimal Number	Binary Equivalent
0	0
1	1
2	10
4	100
12	1100
100	1100100
1995	11111001011

Binary numbers are used by computers because they can easily be represented and stored by device hardware that utilizes switches, magnetic fields, or charge polarities that are normally in one of two states. The on or off, north or south, or positive or negative states can easily represent the 1s and 0s of a binary number, respectively.

Binder:

The polymer used to bind magnetic particles together and adhere them to the tape substrate. Generally, a polyester or polyether polyurethane based system. See polymer.

Bit:

A single numeric character. Each bit of a binary number can either be 0 or 1. An n-bit number is composed of exactly n numeric characters. An n-bit binary number can have 2n distinct values. For example, an 8-bit binary number has 28 = 256 distinct values, namely all the numbers between 00000000 (0 in decimal) and 11111111 (255 in decimal), inclusive. 8-bit quantization would discretely sample a signal and assign each sampling a value between 0 and 255, permitting 256 possible values.

Blocking:

The sticking together or adhesion of successive windings in a tape pack. Blocking can result from (1) deterioration of the binder, (2) storage of tape reels at high temperatures, and/or (3) excessive tape pack stresses.

Cinching:

The wrinkling, or folding over, of tape on itself in a loose tape pack. Normally occurs when a loose tape pack is stopped suddenly, causing outer tape layers to slip past inner layers, which in turn causes a buckling of tape in the region of slip. Results in large dropouts or high error rates.

Coercivity:

The level of demagnetizing force that would need to be applied to a tape or magnetic particle to reduce the remanent magnetization to zero. A demagnetizing field of a level in excess of the coercivity must be applied to a magnetic particle in order to coerce it to change the direction of its magnetization. Coercivity is the property of a tape that indicates its resistance to demagnetization and determines the maximum signal frequency that can be recorded by a tape. Hc is the common abbreviation for coercivity.

Cohesive force:

The force that holds a material together. The force that holds a material to itself.

Cohesiveness:

See cohesive force.

Curvature error:

A change in track shape that results in a bowed or S-shaped track. This becomes a problem if the playback head is not able to follow the track closely enough to capture the information.

dB:

See decibel.

Decibel:

The unit of measure used to indicate relative changes in signal intensity or sound volume. The actual expression for calculating the difference in decibels between signal A and signal B is:

• decibel (dB) = 20·logbase10 (signal A amplitude/signal B amplitude)
• +6 dB represents a doubling of the signal or a 100% increase
  
• +5 dB represents a 78% increase
  
• +4 dB represents a 58% increase
  
• +3 dB represents a 41% increase
  
• +2 dB represents a 26% increase
  
• +1 dB represents a 12% increase
  
• +0 dB represents no change-signals are equal
  
• -1 dB represents a 11% decrease
  
• -2 dB represents a 21% decrease
  
• -3 dB represents a 29% decrease
  
• -4 dB represents a 37% decrease
  
• -5 dB represents a 44% decrease
  
• -6 dB represents a halving of the signal or a 50% decrease

Digital recording:

A recording in which binary numbers are written to the tape that represent quantized versions of the voltage signals from the recording microphone or the video camera. On playback, the numbers are read and processed by a digital-to-analog converter to produce an analog output signal.

Digital-to-analog:

The process in which a series of discrete binary integers is converted to a continuous analog signal.

Dropout:

Brief signal loss caused by a tape head clog, defect in the tape, debris, or other feature that causes an increase in the head-to-tape spacing. A dropout can also be caused by missing magnetic material. A video dropout generally appears as a white spot or streak on the video monitor. When several video dropouts occur per frame, the TV monitor will appear snowy. The frequent appearance of dropouts on playback is an indication that the tape or recorder is contaminated with debris and/or that the tape binder is deteriorating.

Flange pack:

A condition where the tape pack is wound up against one of the flanges of the tape reel.

Format:

The arrangement of information tracks on a tape as prescribed by a standard. The two most common categories of recording formats are longitudinal and helical scan.

Head clog:

Debris trapped in the playback head of a video recorder. Clogging of the playback head with debris causes dropouts.

Helical scan recording:

The recording format in which a slow moving tape is helically wrapped 180° around a rapidly rotating drum with a small embedded record head. The tape is positioned at a slight angle to the equatorial plane of the drum. This results in a recording format in which recorded tracks run diagonally across the tape from one edge to the other. Recorded tracks are parallel to each other but are at an angle to the edge of the tape.

Hydrolysis:

The chemical process in which scission of a chemical bond occurs via reaction with water. The polyester chemical bonds in tape binder polymers are subject to hydrolysis, producing alcohol and acid end groups. Hydrolysis is a reversible reaction, meaning that the alcohol and acid groups can react with each other to produce a polyester bond and water as a by-product. In practice, however, a severely degraded tape binder layer will never fully reconstruct back to its original integrity when placed in a very low-humidity environment.

Hygroscopic:

The tendency of a material to absorb water. An effect related to changes in moisture content or relative humidity. The hygroscopic expansion coefficient of a tape refers to its change in length as it takes up water upon an increase in the ambient relative humidity.

Longitudinal recording:

A recording format in which a slow or fast moving tape is passed by a stationary recording head. The recorded tracks are parallel to the edge of the tape and run the full length of the tape.

Lubricant:

A component added to the magnetic layer of a tape to decrease the friction between the head and the tape.

Magnetic particles:

The magnetic particles incorporated in the binder to form the magnetic layer on a magnetic tape. Iron oxide, chromium dioxide, barium ferrite, and metal particulate are various examples of magnetic pigment used in commercial tapes. The term pigment is a carry over of terminology from paint and coating technology - the magnetic coating on a tape is analogous to a coat of paint in which the magnetic particle is the paint pigment.

Magnetic pigment:

See magnetic particles.

Magnetic remanence:

The strength of the magnetic field that remains in a tape or magnetic particle after it is (1) exposed to a strong, external magnetic field and (2) the external field is removed. The property of a tape that determines its ability to record and store a magnetic signal. Mr is the common abbreviation for magnetic remanence. Magnetic remanence, Mr, and magnetic retentivity, Br, both refer to the ability of the tape to retain a magnetic field; however the latter is expressed in units of magnetic flux density.

Magnetic retentivity:

See magnetic remanence.

Mistracking:

The phenomenon that occurs when the path followed by the read head of the recorder does not correspond to the location of the recorded track on the magnetic tape. Mistracking can occur in both longitudinal and helical scan recording systems. The read head must capture a given percentage of the track in order to produce a playback signal. If the head is too far off the track, recorded information will not be played back.

NARA:

The abbreviation for National Archives and Records Administration.

Pack slip:

A lateral slip of selected tape windings causing high or low spots (when viewed with tape reel laying flat on one side) in an otherwise smooth tape pack. Pack slip can cause subsequent edge damage when the tape is played, as it will unwind unevenly and may make contact with the tape reel flange.

PET:

Abbreviation for polyethylene terephthalate. The polymeric substrate material used for most magnetic tapes.

Polymer:

A long organic molecule made up of small, repeating units (literally, many mers). Analogous to a freight train, where each individual unit is represented by a freight car. At very high magnification, a chunk of polymer would resemble a bowl of cooked spaghetti. Plastic materials are polymers. The strength and toughness of plastics is due, in part, to the length of its polymer molecules. If the chains (links in the freight train) are broken by hydrolysis, the shorter chains will impart less strength to the plastic. If enough polymer chains are broken, the plastic will become weak, powdery, or gooey. See binder.

Popped strand:

A strand of tape protruding from the edge of a wound tape pack.

Print through:

The condition where low frequency signals on one tape winding imprint themselves on the immediately adjacent tape windings. It is most noticeable on audio tapes where a ghost of the recording can be heard slightly before the playback of the actual recording.

Quantization:

A process in which a continuous signal is converted to a series of points at discrete levels. The quantized version of a ramp, a continuum of levels, would be a staircase, where only certain distinct levels are allowed.

Refreshing:

This term can refer to periodic retensioning of tape, or the rerecording of recorded information onto the same tape (or different tape) to refresh the magnetic signal. In the audio/video tape community, refreshing generally refers to retensioning of the tape, but it can also refer to the copying of one tape to another. See transcription.

Relative humidity (RH):

The amount of water in the air relative to the maximum amount of water that the air can hold at a given temperature.

Restoration:

The process where a tape degraded by age is temporarily or permanently restored to a playable condition. The tape backing procedure is an example of a tape restoration procedure.

Retensioning:

The process where a tape is unspooled onto a take-up reel and then rewound at a controlled tension and speed. In performing this procedure, tape pack stresses are redistributed and, thus, the tape is retensioned. This has sometimes been referred to as refreshing (or exercising the tape).

RH:

The abbreviation for relative humidity.

Room ambient conditions:

The temperature, humidity, and air quality of the surrounding conditions. Those conditions generally found in a library, resource, studio, or office facility with a controlled environment (heating and air conditioning), which should range between 66 to 78° F (19 To 26° C) and 30 to 70% relative humidity year round. Analogous to room temperature conditions, except that this term only refers to the temperature of the room.

Scission:

The process in which a chemical bond in a molecule is broken either by reaction with another molecule, such as water, or by the absorption of a high energy photon.

Signal-to-noise ratio:

The ratio of the recorded signal level to the tape noise level normally expressed in decibels. Commonly abbreviated as S/N.

SMPTE:

Abbreviation for the Society of Motion Pictures and Television Engineers.

Stick slip:

The process in which (1) the tape sticks to the recording head because of high friction; (2) the tape tension builds because the tape is not moving at the head; (3) the tape tension reaches a critical level, causing the tape to release from and briefly slip past the read head at high speed; (4) the tape slows to normal speed and once again sticks to the recording head; (5) this process is repeated indefinitely. Characterized by jittery movement of the tape in the transport and/or audible squealing of the tape.

Sticky shed:

The gummy deposits left on tape path guides and heads after a sticky tape has been played. The phenomenon whereby a tape binder has deteriorated to such a degree that it lacks sufficient cohesive strength so that the magnetic coating sheds on playback. The shedding of particles by the tape as a result of binder deterioration that causes dropouts on VHS tapes.

Sticky tape:

Tape characterized by a soft, gummy, or tacky tape surface. Tape that has experienced a significant level of hydrolysis so that the magnetic coating is softer than normal. Tape characterized by resinous or oily deposits on the surface of the magnetic tape.

Stress:

Force per unit area, such as pounds per square inch (psi). A tape wound on a reel with high tension results in a tape pack with a high interwinding stress. See tension.

Substrate:

Backing film layer that supports the magnetic layer in a magnetic tape. PET is currently the most commonly used tape substrate.

Tape baking:

A process in which a magnetic tape is placed at an elevated temperature for a brief time in order to firm up the tape binder. This procedure is recommended as a temporary cure for the sticky shed or sticky tape syndrome. The tape baking procedure is discussed in the reference, "Sticky Shed Syndrome - Tips on Saving Your Damaged Master Tapes," Mix, May 1990, p. 148.

Tape noise:

A magnetic signal on the tape resulting from the finite size and nonuniform distribution of magnetic particles in the magnetic layer of the tape. Tape noise is inherent in any magnetic tape but can be reduced by using smaller pigment sizes in tape formulations. The iron oxide pigments found in less expensive tapes have the largest tape noise level. Ranked in size: iron oxide > chromium dioxide > metal particulate > barium ferrite. Therefore, ranked in order of tape noise: iron oxide > chromium dioxide > metal particulate > barium ferrite.

Tape pack:

The structure formed by and comprised solely of tape wound on a hub or spindle; a tape reel consists of a tape pack, the metal, plastic, or glass hub, and flanges.

Tape transport:

The mechanics used to guide and move the tape through the recording system and past the read and write heads of the recorder. The tape transport consists of the tape guide pins, capstan, rollers, tension controllers, etc.

Tension:

Force, or force per tape width. The force on a tape as it is transported through a recorder. A tape wound on a reel with high tension results in a tape pack with a high interwinding stress. See stress.

Thermal:

An effect related to changes in temperature. The thermal expansion coefficient of a tape refers to its change in length upon a change in the ambient temperature.

Track angle:

The angle that the track of a helical scan recording makes to the edge of the tape. This should correspond with the scan angle of the helical recorder - the angle that the tape makes to the equatorial plane of the rotating drum head. If the track angle and scan angle do not correspond, mistracking will occur.

Transcription:

The process of copying all of the information on one tape to another tape of the same or different format. The term refreshing is commonly used by some archivists and librarians to refer to the process of copying information from one tape to a newer tape of the same format (e.g., VHS to VHS). When the information is copied to a different format (e.g., BetaMax to VHS), the terms reformatting and converting have been used.

Trapezoidal error:

A change in the angle of a recorded helical scan track. Can result in mistracking.

Vinegar syndrome:

Characteristic of the decomposition of acetate based magnetic tape where acetic acid is a substantial by-product that gives the tape a vinegar-like odor. After the onset of the vinegar syndrome, acetate tape backings degrade at an accelerated rate - the hydrolysis of the acetate is catalyzed further by the presence of acetic acid by product.

Solving The Data Loss Mystery: Data Recovery Prevention

Data loss is one of computing's most misunderstood concepts. A user is suddenly unable to access information and is suspended in a state of confusion and panic, wondering, where their data went, and what to do to get it back? What caused the data loss? What could have been done to prevent it? By examining data loss causes, technicians can offer prevention tips, and give users the information they need to adequately minimize the chances of data loss.

What Is Data Loss?

Lost data is data that has become inaccessible to the user. Confusion arises because the industry often presents "lost data" as data that has been permanently destroyed, with no hope for recovery. In reality, findings reveal approximately 85 per cent of lost data can be retrieved. While data may be inaccessible to users, experts are able to recover it using the proper techniques and tools. Unfortunately, hundreds of thousands of gigabytes of data have been lost simply because users were not aware of their options and gave up hope of recovery. Despite technological advances in the reliability of magnetic storage media, the incidence of data loss continues to rise. Data storage remains a fragile science, and data's susceptibility to damage from both natural and human sources remains high.

Here are some data protection tips:

• Have a "fire drill." Back up data and test restore capabilities on a regular basis.
• Keep your computer in a dry, controlled environment.
• Only entrust your data to someone who has the training to properly maintain/repair it.
• Use diagnostic/repair utilities with caution.
• Use anti-virus software and update it as frequently as possible.
• Check all incoming diskettes for viruses.
• Immediately turn off your computer if it begins making an unusual noise. Further operation may damage it beyond repair.

If you have lost data or your drive fails, contact CBL Data Recovery http://www.cbltech.com. They are a leading provider of emergency computer data recovery services for clients experiencing data loss due to hardware failure, natural disaster or software corruption. With more than 10 years experience, CBL Data Recovery offers data recovery services throughout north america with its network of labs, offices and authorized partners.

RAID Array & Server Glossary Of Computer Terms

-- A --

Array

Multiple disk drives configured to behave as a single, independent disk drive. See also Disk Array.

-- B --

Background Initialization

Where the initialization process of a disk array takes place in the background, allowing use of a disk array within seconds instead of several hours. Also known as Immediate RAID Availability.

Benchmarks

A set of conditions or criteria against which a product or system is measured. Computer trade magazine laboratories frequently test and compare several new computers or computer devices against the same set of application programs, user interactions, and contextual situations. The total context against which all products are measured and compared is referred to as the benchmark. Programs can be specially designed to provide measurements for a particular operating system or application.

Berkeley RAID Levels

A family of disk array protection and mapping techniques described by Garth Gibson, Randy Katz, and David Patterson in papers written while they were performing research into I/O systems at the University of California at Berkeley. There are six Berkeley RAID levels, usually referred to as RAID Level 0 through RAID Level 5. See also RAID Levels.

Bridge RAID Controller

A device appearing as a single ID in a Storage Area Network (SAN), but which bridges to multiple devices, typically used to control external RAID subsystems (compare to Internal PCI-based RAID subsystems, see Internal RAID Controller). A bridge RAID controller is often referred to as an External RAID Controller.

-- C --

Cache

A temporary storage area for frequently accessed or recently accessed data. Cache is used to speed up data transfer to and from a disk. See also Caching.

Cache Flush

Refers to an operation where all unwritten blocks in a Write-Back Cache are written to the target disk. This operation is necessary before powering down the system.

Cache Line Size

Represents the size of the data "chunk" that will be read or written at one time, and is set in conjunction with stripe size. Under RAID EzAssistTM, the cache line size (also known as Segment Size) should be based on the stripe size you selected. The default segment size for Mylex RAID controllers is 8K. See also Stripe Size.

Caching

Allows data to be stored in a pre-designated area of a disk or RAM. Caching speeds up the operation of RAID systems, disk drives, computers and servers, or other peripheral devices. See also Cache.

Conservative Cache

An operating mode in which system drives configured with the Write-Back Caching policy are treated as though they were configured for Write-Through operation and the cache is flushed.

Consistency Check

A process that verifies the integrity of redundant data. A consistency check on a RAID 1 or RAID 0+1 configuration (mirroring) checks if the data on drives and their mirrored pair are exactly the same. For RAID Level 3 or RAID Level 5, a consistency check calculates the parity from the data written on the disk and compares it to the written parity. A consistency check from Mylex utilities such as Global Array ManagerTM (GAM) or RAID EzAssistTM give the user the ability to have a discrepancy reported and corrected. See also Parity Check.

Controller

An adapter card, RAID controller, or other module that interprets and controls signals between a host and a peripheral device.

-- D --

Degraded Mode

A RAID mode used when a component drive has failed.

Disk

A non-volatile, randomly addressable, re-writable data storage device, including rotating magnetic and optical disks as well as solid-state disks or other electronic storage elements.

Disk Array

A collection of disks from one or more commonly accessible disk systems. Disk arrays, also known as RAID, allow disk drives to be used together to improve fault tolerance, performance, or both. Disk arrays are commonly used on servers and are becoming more popular on desktops and workstations. See also Array.

Disk Drive

A device for the electronic digital storage of information.

Disk Failure Detection

A RAID controller automatically detects SCSI disk failures. A monitoring process running on the controller checks, among other things, elapsed time on all commands issued to disks. A time-out causes the disk to be "reset" and the command to be retried. If the command times out again, the controller could take the disk "offline." Mylex DAC960 controllers also monitor SCSI bus parity errors and other potential problems. Any disk with too many errors will also be taken "offline." See also Offline.

Disk Traveling, Drive Traveling

A process that occurs when the drives are placed in a different order than the original order. Disk traveling can occur whether or not a drive has failed.

Disk System

A storage system capable of supporting only disks.

Drive Groups, Drive Packs

A group of individual disk drives (preferably identical) that are logically tied to each other and are addressed as a single unit. In some cases this may be called a drive "pack" when referring to just the physical devices.

All the physical devices in a drive group should have the same size; otherwise, each of the disks in the group will effectively have the capacity of the smallest member. The total size of the drive group will be the size of the smallest disk in the group multiplied by the number of disks in the group. For example, if you have 4 disks of 400MB each and 1 disk of 200MB in a pack, the effective capacity available for use is only 1000MB (5x200), not 1800MB.

Dual Active

A pair of components, such as storage controllers in a failure tolerant storage system, that share a task or set of tasks when both are functioning normally. When one component of the pair fails, the other takes the entire load. Dual active controllers (also called Active/Active controllers) are connected to the same set of devices and provide a combination of higher I/O performance and greater failure tolerance than a single controller.

-- E --

ECC

Error Correcting Code, a method of generating redundant information which can be used to detect and correct errors in stored or transmitted data.

Embedded Storage Controller

An intelligent storage controller that mounts in a host computer's housing and attaches directly to a host's memory bus with no intervening I/O adapter or I/O bus.

External RAID Controller

A RAID controller in its own enclosure, rather than incorporated into a PC or server. External RAID controllers are often referred to as a Bridge RAID Controller. Mylex SANArray FL, FF, FFx, and Pro FF2 controllers are external RAID controllers. Compare with Internal RAID Controller.

-- F --

Failback

Restoring a failed system component's share of a load to a replacement component.

Failover

A mode of operation for failure tolerant systems in which a component has failed and a redundant component has assumed its functions.

Failover Port

A fibre channel port capable of assuming I/O requests for another, failed port on the loop. During normal operation, a failover port may be active or inactive. Failover ports assume the same loop ID and, optionally, the same node from the failed port.

Failure

A detectable physical change in hardware, requiring replacement of the component.

Fault Tolerance, Failure Tolerance

The ability of a system to continue to perform its function even when one of its components has failed. A fault tolerant system requires redundancy in disk drives, power supplies, adapters, controllers, and cabling. Mylex RAID controllers offer high levels of fault tolerance.

Fibre Channel

Technology for transmitting data between computer devices at a data rate of up to 2 Gbps (two billion bits per second), especially suited for connecting computer servers to shared storage devices and for interconnecting storage controllers and drives.

Fibre Channel is expected to replace the Small System Computer Interface (SCSI) as the transmission interface between servers and clustered storage devices. It is also more flexible: devices can be as far as ten kilometers (about six miles) apart. The longer distance requires optical fiber as the physical medium; however, fibre channels also work using coaxial cable and ordinary telephone twisted pair wires.

Flash ROM

Memory on an adapter containing software that can be reprogrammed without removing it from the board.

-- G --

Global Spare

An extra, physical disk drive placed in an array and used as a Hot Spare. A global spare automatically takes the place of a failed drive. See also Auto Swap.

-- H --

Host

Any computer system to which disks are attached and accessible for data storage and I/O.

Hot Replacement of Disks

The design of all Mylex controllers allows for the replacement of failed hard disk drives without interruption of system service. In the event of a SCSI drive failure on a properly configured system (where the data redundancy features of the controller are used), the system generates a message to alert the system operator.

When a replacement drive becomes available, the system operator can remove the failed disk drive, install a new disk drive, and instruct the controller to "rebuild" the data on the new drive, all without interrupting system operations. Once the rebuild is complete, the controller will be brought back into a fault tolerant state. See also Hot Swap.

Hot Spare

A physical disk drive not part of a system drive that the controller can use to automatically rebuild a critical system drive. The hot spare drive must have at least as much capacity as the largest disk drive in the array or the rebuild may not start. See also Hot Standby and Standby Replacement of Disks.

Hot Standby

A redundant component in a fault tolerant storage system that has power applied and is ready to operate, but which does not perform its task as long as the primary component for which it is standing by is functioning properly. See also Hot Replacement of Disks and Hot Spare.

-- I --

Immediate RAID Availability

See Background Initialization

In-Line Terminator

A plug attached to the end of a SCSI cable in order to initiate active termination. Used when SCSI devices on the cable do not have built-in termination. See also Active Termination.

Interface

A hardware or software protocol that manages the exchange of data between the hard disk drive and the computer. The most common interfaces for small computer systems are ATA (also known as IDE) and SCSI.

Internal RAID Controller

A controller circuit board that resides inside a computer or server. An internal RAID controller resides on a bus, such as the PCI bus. Examples of internal RAID controllers include the Mylex AcceleRAID and eXtremeRAID families.

-- J --

JBOD

Just A Bunch of Disks (Drives), a number of disk drives, usually in an enclosure. JBOD implies that the disks do not use RAID technology and function independently. All Mylex RAID controllers support JBOD mode.

-- K --

-- L --

Latency

1. The time between the making of an I/O request and completion of the request's execution. 2. Short for rotational latency, the time between the completion of a seek and the instant of arrival of the first block of data to be transferred at the disk's read/write head.

Logical Drive

The logical devices presented to the operating system. System drives are presented as available disk drives, each with a capacity specified by the Mylex RAID controller. See also Storage Device.

-- M --

Mirrored Cache

A cache memory that has duplicate data from another controller. In the event of failure of the original controller, the second controller can take the cached data and place it on the disk array.

Mirrored Hard Drive

Two hard drives the computer sees as one unit. Information is stored simultaneously on each drive. If one hard disk drive fails, the other contains all of the cached data and the system can continue operating.

Mirroring

The complete duplication of data on one disk drive to another disk drive, this duplication occurs simultaneously with each write operation: each disk will be the mirror image of the other (also known as RAID Level 1, see RAID Levels). All Mylex RAID controllers support mirroring.

-- N --

-- O --

-- P --

Parity

A method of providing complete data redundancy while requiring only a fraction of the storage capacity of mirroring. The data and parity blocks are divided between the disk drives in such a way that if any single disk drive is removed or fails, the data on it can be reconstructed using the data on the remaining disk drives. The parity data may exist on only one disk drive or be distributed between all disk drives in a RAID group. See also Rotated XOR Redundancy.

Parity Check

A function used to verify the integrity of data on a system drive. It verifies that mirror or parity information matches the stored data on the redundant arrays. If the parity block information is inconsistent with the data blocks, the controller corrects the inconsistencies. See also Consistency Check.

Partitioning

Where the full usable storage capacity of a disk or array of disks appears to an operating environment in the form of several virtual disks whose entire capacity approximates that of the underlying disk or array.

PCI Hot Plug

A feature that allows for the printed circuit board (PCB) to be replaced without powering down the entire system-an essential feature in newer PCI-based PCs. Mylex DAC960PG, DAC960PJ, AcceleRAID, and eXtremeRAID products are all PCI Hot Plug compatible. See also Hot Plug.

-- Q --

-- R --

RAID

Redundant Array of Independent Disks, a collection of two or more disks working together in an array. Mylex RAID controllers implement this technology to connect up to 15 SCSI devices per channel. The different forms of RAID implementation are known as "RAID levels." See also Berkeley RAID Levels, Disk Array, and RAID Levels.

The system manager or integrator selects the appropriate RAID level for a system. This decision will be based on which of the following are to be emphasized:

• Disk Capacity
• Data Availability (redundancy or fault tolerance)
• Disk Performance

RAID Adapters

See RAID Controller

RAID Advisory Board (RAB)

An association of companies whose primary intention is to standardize RAID storage systems. Mylex is a member of RAB.

RAID Controller

Low cost RAID controllers that use SCSI channels on the motherboard.

RAID Levels

Mylex disk array controllers support four RAID Advisory Board approved (RAID 0, RAID 1, RAID 3, and RAID 5), two special (RAID 0+1, and JBOD), and three spanned (RAID 10, 30, and 50) RAID levels. All DAC960, AcceleRAID, and eXtremeRAID series controllers support these RAID levels. See also Berkeley RAID Levels.

Level 0:

Provides block "striping" across multiple drives, yielding higher performance than is possible with individual drives. This level does not provide any redundancy.

Level 1:

Drives are paired and mirrored. All data is 100 percent duplicated on a drive of equivalent size.

Level 3:

Data is "striped" across several physical drives. Maintains parity information, which can be used for data recovery.

Level 5:

Data is "striped" across several physical drives. For data redundancy, drives are encoded with rotated XOR redundancy.

Level 0+1:

Combines RAID 0 striping and RAID 1 mirroring. This level provides redundancy through mirroring.

JBOD:

Sometimes referred to as "Just a Bunch of Drives." Each drive is operated independently like a normal disk controller, or drives may be spanned and seen as a single drive. This level does not provide data redundancy.

Level 10:

Combines RAID 0 striping and RAID 1 mirroring spanned across multiple drive groups (super drive group). This level provides redundancy through mirroring and better performance than Level 1 alone.

Level 30:

Data is "striped" across multiple drive groups (super drive group). Maintains parity information, which can be used for data recovery.

Level 50:

Data is "striped" across multiple drive groups (super drive group). For data redundancy, drives are encoded with rotated XOR redundancy.

Note: The host operating system drivers and software utilities remain unchanged regardless of the level of RAID installed. The controller makes the physical configuration and RAID level implementation.

RAID Migration

A feature in RAID subsystems that allows for changing a RAID level to another level without powering down the system.

Read-Ahead Cache

A caching strategy whereby the computer anticipates data and holds it in cache until requested.

Recovery

The process of reconstructing data from a failed disk using data from other drives.

Redundancy

The inclusion of extra components of a given type in a system (beyond those the system requires to carry out its functions).

Rotated XOR Redundancy

XOR refers to the Boolean "Exclusive-OR" operator. Also known as Parity, a method of providing complete data redundancy while requiring only a fraction of the storage capacity of mirroring. In a system configured under RAID 3 or RAID 5 (which require at least three SCSI drives), all data and parity blocks are divided amongst the drives in such a way that if any single drive is removed (or fails), the data on it can be reconstructed using the data on the remaining drives. In any RAID 3 or RAID 5 array, the capacity allocated to redundancy is the equivalent of one drive.

-- S --

SAF-TE

SCSI Accessed Fault-Tolerant Enclosure, an "open" specification designed to provide a comprehensive standardized method to monitor and report status information on the condition of disk drives, power supplies, and cooling systems used in high availability LAN servers and storage subsystems. The specification is independent of hardware I/O cabling, operating systems, server platforms, and RAID implementation because the enclosure itself is treated as simply another device on the SCSI bus. Many other leading server, storage, and RAID controller manufacturers worldwide have endorsed the SAF-TE specification. Products compliant with the SAF-TE specification will reduce the cost of managing storage enclosures, making it easier for a LAN administrator to obtain base-level fault-tolerant alert notification and status information. All Mylex RAID controllers feature SAF-TE.

Sector

The unit in which data is physically stored and protected against errors on a fixed-block architecture disk.

Segment Size

See Cache Line Size

Sequential I/O

A type of read and write operation where entire blocks of data are accessed one after another in sequence, as opposed to randomly.

SES

SCSI Enclosure Services, a standard for SCSI access to services within an enclosure containing one or more SCSI devices. For disk drives, power supplies, cooling elements, and temperature sensors, the actions performed are the same as for SAF-TE monitoring. If a UPS is connected to any SES-monitored enclosures, and an AC failure or two minute warning is reported, conservative cache is enabled and all system drives are switched to write-through cache. Primarily used in fibre enclosures.

Session

The period of time between any two consecutive system shutdowns; system shutdown may be either a power off/on, or a hardware reset.

SMART

Self-Monitoring Analysis and Reporting Technology, the industry standard reliability prediction indicator for both the ATA/IDE (advanced technology attachment/integrated drive electronics) and SCSI hard disk drives. Hard disk drives with SMART offer early warning of some hard disk failures so critical data can be protected.

Spanning

A process that provides the ability to configure multiple drive packs or parts of multiple drive packs. In effect, spanning allows the volume used for data processing to be larger than a single drive. Spanning increases I/O speeds, however, the probability of drive failure increases as more drives are added to a drive pack. Spanned drive packs use striping for data processing. See also Striping and Drive Groups, Drive Packs.

Standard Disk Drive

This term refers to a hard disk drive with SCSI, IDE, or other interface, attached to the host system through a standard disk controller.

Standby Replacement of Disks

See also Hot Spare. One of the most important features the RAID controller provides to achieve automatic, non-stop service with a high degree of fault-tolerance. The controller automatically carries out the rebuild operation when a SCSI disk drive fails and both of the following conditions are true:

• A "standby" SCSI disk drive of identical size is found attached to the same controller;
  
  
• All of the system drives that are dependent on the failed disk are redundant system drives, e.g., RAID 1, RAID 3, RAID 5, and RAID 0+1.
  
  

Note: The standby rebuild will only happen on the same DAC960 controller, never across DAC960 controllers.

During the automatic rebuild process, system activity continues as normal. System performance may degrade slightly during the rebuild process.

To use the standby rebuild feature, you should always maintain a standby SCSI disk in your system. When a disk fails, the standby disk will automatically replace the failed drive and the data will be rebuilt. The system administrator can disconnect and remove the bad disk and replace it with a new disk. The administrator can then make this new disk a standby.

The standby replacement table has a limit of 8 automatic replacements in any session (from power-on/reset to the next power-off/reset). When the limit of 8 is reached and a disk failure occurs, the standby replacement will occur but will not be recorded in the replacement table.

To clear the "standby replacement" table, reboot the system from a DOS bootable floppy, run the configuration utility and select the option 'view/update configuration' from the main menu. A red box labeled 'Drive Remap List' will be displayed. Selecting the box will allow you to continue. You should save the configuration without making any changes, and exit the configuration utility. This will clear the replacement table. You may now proceed to boot your system and continue normal operations.

In normal use, the replacement table limit of 8 should not cause any problems. Assuming that a disk fails about once a year (drives we support generally come with a 5-year warranty), the system would run continuously for a minimum of 8 years before the table would need to be cleared.

Storage Device

A collective term for disks, tape transports, and other mechanisms capable of non-volatile data storage.

Stripe Order

The order in which SCSI disk drives appear within a drive group. This order must be maintained, and is critical to the controller's ability to "rebuild" failed drives.

Stripe Size

The size, in kilobytes (1024 bytes) of a single I/O operation. A stripe of data (data residing in actual physical disk sectors, which are logically ordered first to last) is divided over all disks in the drive group.

Stripe Width

The number of striped SCSI drives within a drive group.

Striping

The storing of a sequential block of incoming data across multiple SCSI drives in a group. For example, if there are 3 SCSI drives in a group, the data will be separated into blocks. Block 1 of the data will be stored on SCSI drive 1, block 2 on SCSI drive 2, block 3 on SCSI drive 3, block 4 on SCSI drive 1, block 5 on SCSI drive 2, and so on. This storage method increases the disk system throughput by ensuring a balanced load among all drives.

Sub-System Storage

A collection of disks providing data storage space to a system user.

-- T --

Terminator

A part used to end a SCSI bus.

Termination

A method of matching transmission impedance of a bus to eliminate signal reflections from the physical ends of the bus.

Throughput

The number of I/O requests satisfied per unit of time (usually per second).

TPC-C, Tpm-C

The Transaction Processing Performance Council (TPC) is a standards organization that measures transaction throughput of systems. One of their benchmarks is Tpm-C, which reflects price and performance metrics. TPC-C reflects new order transaction rate, a benchmark for transaction speed. Mylex products have won consistently high TPC-C results.

Transfer Rate

The rate at which data moves between the host computer and storage, input, or output devices, usually expressed as a number of characters per second.

-- U --

-- V --

-- W --

Write-Back Cache

A caching strategy whereby write operations result in a completion signal being sent to the host operating system as soon as the cache (not the disk drive) receives the data to be written. The target disk drive will receive the data at a more appropriate time in order to increase controller performance. An optional cache battery backup can be used to protect against data loss as a result of a power failure or system crash.

Write-Through Cache

A caching strategy whereby data is written to the SCSI drive before a completion status is returned to the host operating system. This caching strategy is considered more secure, since a power failure will be less likely to cause loss of data. However, a write through cache results in a slightly lower performance.

-- X --

XOR

Exclusive "Or", a computer language function that generates parity in RAID systems; "this or that but not both."

-- Y --

-- Z --

Protecting Your Bottom Line With Good Data Recovery Planning

Sometimes, a day can seem like a lifetime.

When critical business data is lost, every minute that goes by means missing information, lost opportunities, and perhaps even the closing of a successful institution or department. Whatever the cause of the data loss - disk crash, power outage, virus, or even accidental deletion - the usual result is that gigabytes of files and weeks, or even months, of work are lost.

The primary key to ensuring ongoing survival in the face of data loss is the development and implementation of an appropriate business continuity plan. The second key is the employment of the requisite technology.

A business continuity plan documents which organizational functions are critical, what steps are necessary to survive without them, and what resources are available to help recover lost or damaged systems. Without a suitable continuity plan, data loss might be irrevocable. In a world that's defined by access to data, irreversible data loss is simply unacceptable.

In an increasingly volatile environment, institutions that want to stay efficient can't afford to have their systems down for even a short period of time. A recent report by Gartner Group Inc. says organizations will need to reduce the time it takes to recover critical processes and application systems to 24 hours by 2003. Even non-critical systems, the report says, will need to be back up in four days.

It's a simple choice, really. You can back up your hard disk or risk losing your data, your setup, and your applications. Whatever method you choose, it's important that you put a business continuity plan in place and use it.

It's a fact that continuity planning can itself be an onerous task, requiring extensive thought and comprehensive implementation. Each plan must be designed to meet the particular needs and requirements of the institution.

The first step in protecting information assets is to identify the organization's most important assets and information. During this phase of planning, threats and vulnerabilities are identified, solutions are proposed and refined, corporate policies are clarified, roles and responsibilities are assigned, and standards and training are developed.

The second step is the creation of a security plan, with its own procedures, budget, and implementation timetable. Once those steps are complete, new architecture can be rolled out and new procedures put in place. The new system should then be tested from the outside for any remaining weak points. Finally, security should be audited on a regular basis to keep pace with both internal changes and evolving external threats.

Such a continuity plan provides the map, but it remains for each organization to actually make the security journey. Senior management must support the project and demonstrate their involvement. Business and technical experts must be involved on an ongoing basis. Individual business units within the organization must take responsibility for their own security assessments.

Behind the business continuity plan, of course, lies the strength of appropriate technology. If protecting the organization's data is the fundamental priority, suitable backup technologies must be put in place.

Uninterrupted availability is most commonly achieved by the presence of redundant design, clustering, and fail-over with software and firmware support. The bottom line is that IT managers must ensure that all critical components are duplicated, so that system and application availability is maintained in the event of any single component failure.

For a speedy end to system downtime, and to facilitate resumption of business in the face of disaster, the most common facility is the use of remote data mirroring. This means that an exact copy of the business' production data is maintained in a remote site. Should a failure or disaster occur in the original production site, remote mirroring can be used to restart the system and applications within the remote site.

Remote data mirroring can take one of two forms - physical mirroring, based on a replication of the original site's hardware, and logical mirroring, based on a replication of the original system's file structure. Each has its own advantages and benefits, and each will be chosen according to the specific needs of the user.

Physical mirroring will be the appropriate choice when performance, data currency, and ease of management are most important factors for the user. This is because physical mirroring's use of a disk-based system does not consume host system CPUs, requires that only a single I/O be issued for the mirroring operation, allows software mirroring independent of disk technology, and may improve read performance with multiple read devices.

Logical mirroring, on the other hand, will be the more appropriate choice when transactional consistency is a more important factor. Within a logical mirroring solution, remote data corruption is less likely to occur, resynchronization will usually require manual intervention, transactions - and not data blocks - will be mirrored, and the result is slightly lower performance than with a physical mirroring solution.

When considering the choice of a remote mirroring solution, a number of questions need to be answered, so that the results obtained will fit the needs of the organization in the most suitable manner.

Will the mirroring operation be synchronous or asynchronous? How important is data currency in the backup and restore functions? What is the system's (and the organization's) tolerances to some measure of data loss? Should the solution have the ability to maintain changed data information if second fault event occurs? How can the recoverability of data at the remote location be guaranteed?

If the ongoing availability of data is the key to business survival, a remote mirroring solution - whether it is based on a physical or logical system - can literally be the guarantee that essential information can be accessed when needed. Similarly, data replication technologies can provide businesses with guarantees that data is mirrored to a remote site in the event of a site failure. Such technologies replicates, or shadows, the organization's data in real time, and writes the data to alternative sites or systems via a network.

Storage over IP (SoIP) offers another way of ensuring data security. SoIP sends block-level data over an IP network, enabling servers to connect to SCSI storage devices and treat them as if they were directly attached to the server, regardless of their location. It optimizes the organization's ability to enable remote data backup, tape vaulting, and remote disk mirroring. SoIP comes in two flavors, storage tunneling and native IP-based storage, each with its own advantages and disadvantages.

Storage tunneling provides a dedicated, point-to-point link between two SANs via encapsulated Fibre Channel SAN frames in IP packets across an IP network. Storage tunneling generally makes use of existing metropolitan area networks and wide area networks. However, storage tunneling lacks the ability to make full use of standard IP network management and control tools, such as directory services, traffic management, and quality of service.

Native IP-Based storage integrates existing storage protocols with the IP protocol, so that storage traffic can be managed with existing software applications and tools for bandwidth provisioning, traffic management, and overall network management. Native IP-based storage devices allow data to be stored and accessed anywhere the network will reach.

Data snapshots, another technology for ensuring redundancy, are read-only views of the file system. After a snapshot has been taken, changes to files are reflected in updates to the current set of pointers. In basic terms, snapshots take a picture of what the system data looks like, then, as changes are made, makes snapshots of only those changes. The use of data snapshot technology can help organizations minimize costs, because they take up very little disk space and can be sent to remote sites for disaster recovery, thus reducing the need for redundant storage.

In a business environment that's increasingly characterized by globalization, the Internet, and vulnerability to intrusion, solid continuity planning - and the attendant appropriate technology - has become a critical element in business organizations at all levels. The threat of data loss, together with its disagreeable consequences, is, after all, an ever-present danger for everyone.

CD Optical Storage Glossary of Computer Terms

A...

access time:

In mass storage devices, the time elapsed to read or write to or from a device

additive color system:

A color reproduction system in which images are reproduced by mixing appropriate amounts of red, green, and blue lights.

animation:

A synchronized sequence of graphics that conveys action.

antialiasing:

The process of reducing the visibility of jagged edges by using gray scale pixel values to smooth andfeather contrasting intersections of bitmapped objects.

application:

A computer program written for a specific purpose.

aspect ratio:

The ratio of width to height of an image. The standard aspect ratio of broadcast television and mostcomputer displays is 4:3. The 35mm slide standard is 3:2.

asymmetric system:

A video system that requires more equipment to store, process, and compress a digitalimage than it needs to decompress and playback. Intel's DVIand Phillips/Sony's CD-Isystems are asymmetric in full fidelity mode.

audio track:

A CD- DA track with digital audio samples encoded as 16 bit numbers.

audio:

Sound portion of a video signal. or separate soundused to; annotate objects on frames including text, graphics, animation and still images.

authoring language:

A high- level programming language using English or mnemonics and simple commands specifically designed for developing multimedia applications. Often included as a subset of an authoring system.

authoring system:

A software product designed to allow userswithout specific programming skills to develop and test multimedia applications.

averaging:

The process of smoothing the selection or image by averaging the values of the surrounding pixelsover a specified radius.

---

B...

bitmap:

name for a family of image file-types composed ofdots (pixels). Bitmaps have attributes specifying color format, resolution, header, bit order, and other variables. A checker board is a good conceptual model for a bitmap image.

blur:

To distort the current selection or image by reducing contrast along object lines with gradients.

BPP:

Bits Per Pixel. An acronym for the number of bits used to represent the color value of each pixel in a digital image color format. example: CMYK=32bpp, RGB true color =24bpp,256 color & grayscale=8bpp, 16color=4bpp, Black and White line art=1bpp.

brightness & contrast balancing:

The process of adjusting the density and intensity of an image.

---

C...

cache:

Pronounced "cash".An external or internal reserved portion of a computer's electronic memory Random-Access Memory (RAM). Frequently used information is stored in the cache so that your computer can get the information more quickly.

CD:

The 12cm (4.75 in.) optical read only disc used for digital audio, data, and video storage and retrieval in various computer, audio, and video systems. CDs are produced using a number of processes to store information for optical retrieval. see: WORM, WREN, CD-ROM

CD- DA Track:

a track on a compact disc containing audio information encoded according to the CD-Digital Audio specific

CD-I:

Compact Disc Interactive. an interactive audio/video/computer system developed by Sony and Phillips For the consumer market.

CD-ROM:

Compact Disc Read Only Memory. An adaptation of CD technology for use with general digital data. CD-ROM discs are "pressed" in an injection molding process from a master mould to create the data tract. Then they are coated with a reflective material and sealed.

CD-ROM XA

:Compact Disc Read Only Memory Extended Architecture. A format for recording compressed digital audio at lower qualities, allowing capacity increases on a single CD from four to 19 hours.

CD-RTOS:

Kernel:the nucleus of CD-RTOS, which is responsible for service request processing, memory management, system initialization, multi-tasking, input/output management and exception and interrupt processing.

CD-RTOS:

Compact Disc Real-Time Operating System. the name of the operating system used in CD-I players.

CD-WORM:

Compact Disc Write Once Read Many times. A type of CD-ROM disc named for the process used to create data on the disc. CD-WORM Discs preform identically as CD-ROM discs. The difference being a laser is used to "burn" the reflective layer to create the data tract. The cost of " WORM Burning" is considerably less than glass master production for a single disc.CD-WORM Disks can be used to transport CD-ROM s for mastering and replication.

CD-WREM:

Compact Disc Write Read Erase Memory. A data storage system commonly referred to as "Magneto-Optical". It incorporates laser technology to "Burn" a magnetic layer on the disc, this produces a reflective surface that can then be read. This magnetic layer can be burned many times giving the medium read, write, and write over capability not found in CD- ROM & CD-WREM. This advantage comes only with considerable cost for Drives and Disc Cartridges. As a result this technology has not caught on in the home consumer market. It has great potential for multimedia, pre-press publication, and other digital graphic applications.

chroma keying:

facility to replace selected colors in a video image with others that allows the creation of different scenes against the background. Some video boards contain such capabilities.

chrominance:

signals of an image system that represent the color components of the image such as hue and saturation. A black and white image has chrominance value of zero.

clipart:

Stock digital images in various subject matter and format for use in multimedia productions or anywhere graphics are needed. Rights to use, pricing, and quality vary from one manufacturer to another.

clone:

To duplicate a portion of an image to another location. This is a cornerstone to the editing of digital images. This effect is useful in the process of retouching photographs.

CLUT:

Color Look-Up Table. A table containing all the colors that may be used in a particular picture. Each entry provides an RGB value. The picture may then be encoded using the table entry addresses rather than the direct RGB value.

color balancing:

The process of tuning the overall color cast of an image or selection

compression:

a digital process that permits data to be stored or transmitted using less than normal the number of bits. Compression is critical for displaying audio and moving video fast enough on desktop computers. Some compression standards for still images are formulated by JPEG, for moving video by MPEG, and for telecommunications transmission by CCITT.

---

D...

DDE:

Dynamic Data Exchange. A communication technique for Windows and OS/2. DDE Applications can send and receive data once a communication path is established.

diffuse:

To soften contrasting edges and fill areas of an image or object via random patterns. Also used to simulate colors outside the color pallet. see dithering

digital:

A system in which values are represented by a series of binary bits.

digitizing:

the process of encoding or converting images, sound, video and other data from analog or printed form to a digital format/specification.examples: Scanning= Printed image to Digital Image file, video capture=analog video signal to still or motion digital file.

dithering:

The process of using patterns to simulate colors or gradients

DVI:

digital video interactive. This is a compression format for recording digital video on a CD- ROM disk that provides up to 72 minutes of full motion video, or four hours of one-quarter screen full-motion video.

---

E...

EISA:

Extended Industry Standard Architecture. A 32-bit bus architecture standard designed for PC compatibles to take advantage of newer and faster microprocessors. Supports older AT style expansion boards. IBM's Micro Channel Architecture (MCA) does not.

EMS:

Expanded Memory System. A specification developed by the Lotus, Intel and Microsoft (LIM) corporations for application programs to address added memory resources above the 640- kbyte limit of PC and MS-DOS operating system. EMS helps provide maximum performance of memory-intensive applications such as Lotus 1-2-3 and Microsoft Windows.

encoding:

Storing information according to a file specification for an intended retrieval suitability

EPP:

Enhanced Parallel Port.

ESDI:

Enhanced Small Device Interface. A standard for connecting disk drives and tape drives to a computer. This standard enables the drive to transfer data at high speeds.

exclusion:

The opposite of selection. An editing technique to select desired areas of an image by ruling out all undesired areas. Particularly useful in selecting and removing an object from its background.

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F...

fade:

A gradual change in brightness of an image or intensity of a sound. Considered a special effect that can be implemented with software or hardware.

file header:

A block of data in a file, usually at the beginning, which describes the type of data in the file and the format of the data.

film scanning:

Scalable optical Digitization of photographic transparencies negatives and slides. High quality standards requirements for Pre-press Digitization have resulted in capture specs exceeding 48bpp @ 6000pixels.

film recording:

A service used to produce film transparencies from digital images. Recorder specs, vary from one manufacturer to another near 4000pixels for 35mm film @ 24bpp

flash memory:

Flash memory is a nonvolatile memory medium (it "remembers" even when the power is turned off) that can easily be updated. This credit card-sized package will be used to replace floppy and hard disk drives in portable personal computers in the future. Flash memory cards substantially reduce the computer's power consumption (when compared with traditional mechanical disk-drive memories).

flatbed scanning:

Document and image scanning utilizing a level glass bed scanner. Device specifications range include RGB @600dpi,single pass

flicks:

Common term for digital motion sequences

fractal:

Fractional Dimensional. A mathematical definition of a fractional element of an image after repeated application of a specific compression algorithm. Has theoretical compression ratio capability of 10,000:1. Commercial software is available with compression ratios in the range of 2,500:1.

frame:

Used in video to denote a complete scan of an image. In motion video repeated scanning ofa changing scene produces a series of frames. Synonymous with a full computer screen desktop applications.

full-motion video:

Display of a video sequence at the broadcast TV frame rate of 30 fps. Sometimes used to define motion video that is perceived to provide smooth motion regardless of frame rate applied.

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G...

GUI:

Graphical User Interface. A graphically oriented interface that allows direct manipulation of on-screen objects and events using icons, menus and dialog controls. Macintosh, Windows, Silicon Graphics, island productsSee: WIMPs,

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H...

hypermedia:

A multimedia application that lets the user point to objects, images, video, or text to navigate the application.

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I...

IDE:

Integrated Drive Electronics.

IMA:

Interactive Multimedia Association. An umbrella organization grouping over 220 suppliers and end-users to deal with multimedia standards and data exchange issues. Endorses and supervises technical aspects of JPEG and MPEG compression standards and developing multimedia platform standards.

importing:

A method of accessing or bringing in files created on other platforms or applications.

interactivity:

The ability of a user to control the presentation by a multimedia system, not only for material selection, but for the way in which material is presented.

interchange file:

A family of filetypes whose specifications are standardized to facilitate use in a broad range of applications and in some cases platforms.

ISA:

Industry Standard Architecture.

ISDN:

Integrated Services Digital Network. Telecommunications networks based on fiber optics with greatly enhanced transmission capacity for handling video images and applications such as video conferencing.

ISO 9660:

The designated specification number for the file structure standard of CD-ROM adopted by the International Standards Organization.

ISO:

International Standards Organization. A world organization which serves to promote establishment of standards in facilitating international exchange of goods and services and develop mutual cooperation in scientific, technical, intellectual and economic areas of activity. The American National Standards Institute (ANSI) is the current U.S. voice in the ISO.

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J...

JBIG:

Joint Bi-level Imaging Group. A working group established to develop a standard for compressing bi-level images such as black-and-white photographs or pages of text. JBIG is a loss less compression technique.

JPEG:

Joint Photographic Experts Group. A standard for compression algorithms for digitizing still photographic images. JPEG compression ratios may range from 10:1 to 80:1, but it is a continuous trade-off between image quality and speed of delivery and storage capacity. Multimedia platforms are being equipped with special boards or chips implementing JPEG compression standard based on the DCT algorithm. There are also software solutions available to accomplish JPEG compression.

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K...

KBPS:

Kilobits Per Second. A measure of transmission rate in thousands of bits per second commonly referred to as baud rate. Communication channels using telephone modems are established at set bit rates, 300, 1200, 2400, 4800, 9600, 14400 respectively. (example 14.4kbps)

Kodak Photo CD:

A proprietary asymmetric image recording format developed by Eastman Kodak Company and introduced in 1992. The content of the CD disc is composed of nearly 100 24bit images 3000pixel in a multisession configuration. The KODAK Photo CD is considered a milestone in imaging development.

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L...

LAN:

Local Area Network. A local community of computers linked with high performance cables. LANs vary in size, but are always imited to a single geographical area, such as an office, corporation, or campus.

luminance:

Refers to the brightness value of all the points in an image.

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M...

magenta:

The color obtained by mixing equal intensities of red and blue light. It is also the correct name for the subtractive primary color usually called red.

magneto-optical:

See CD-WREM.

mastering:

A real time process in which videotaped materials are used to create a master optical disk that can be replicated into final videodiscs or CD-ROM disks for operation with desktop computers. Usually performed by an outside specialty shop.

media:

Specific means of artistic communication including forms such as film, art, voice, music, sounds, text, programming etc.

MIDI:

Musical Instrument Digital Interface. It is a series of digital bus standards for interfacing of digital musicalinstruments with computers.

morph:

The special effect merging object attributes from multiple images into composite views

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N...

NN

n

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O...

ODB:

Object Database. A database that can handle diverse and complex data including video images, audio, bit maps, graphics and unstructured text.

opacity:

Term used to describe the amount an editing technique effects a given area of an image. Opacity in commonly expressed in percentages an can be used to simulatea watercolor wash or in sequence segments to fade or dissolve

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P...

paint:to apply color or gradient to an area of an image

palette:A group of selected colors used by a graphics board. The EGA board uses a palette of 16 colors. VGA boards in some resolutions provide a palette of 256 colors.

PCI Local Bus:The Peripheral Component Interconnect (PCI) local bus

PCMCIA:Personal Computer Memory Card International Association. PCMCIA is becoming the link between desktop and notebook computing for data transfer and storage. PCMCIA slots perform the same functions as expansion slots on PC compatibles.

Photo CD:Generic term used to refer to Digital images on compact disc (see Kodak Photo CD)

pixel:Picture Element. The smallest element of a screen represented as a point of specific color and intensity level.

platform:The hardware and operating system that applications are run on

premastering:In CD-ROM distribution, the process of preparing the data to be placed on the CD-ROM so that is optimally fits the CD-ROM format and limitations.

primary color:In a tri-stimulus color video system, one of the three colors mixed to produce an image. In additive color systems, the primary colors are red, green, and blue. In subtractive color systems, the primaries are cyan, magenta, and yellow.

production:In video, refers to the process of creating programs. In more specific usage, production is the process of getting original video onto tape or film and ready for post- production.

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Q...

QQ

q

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R...

resampling:

The practice of interpolating an image of one specification and producing an image of another specification from that interpolation.

resolution:

Defines image quality of a display. It refers to the number of pixels available on a display. Resolution controls the level of detail that can be presented on a screen.

retouch:

Digital image editing processes used to restore damaged photographs for reproduction

RLE:

Run-Length Encoding:a data compression technique that records repeated data elements with the same value, which is coded once along with a count of the number of times it occurs.

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S...

scanning:

The most common practice of encoding real images into digital form Accomplished by use of a scanner which passes an image sensor across the original

screen grabs:

Common term for the capturing screen rasterization images and video stills to digital files. Can be preformed with software or hardware, but quality may vary between method used.

SCSI:

Small Computer System Interface. The abbreviation is pronounced "scuzzy." A connection that allows high-speed information transfer between the computer and any external devices at speeds in the range of 4 to 5 megabytes per second. This specification also allows multiple devices to be connected via addresses to a single port (receptacle).

SCSI-II:

A specification developed to provide greater speed and performance. An SCSI-II connection provides transfer rates ranging from 10 to 40 megabytes per second.

selection:

The term for indicating the desired area to be effected by editing.

sharpen:

To increase contrast along object edges to improve image appearance.

SIMM:

Single In-line Memory Module. A small narrow circuit board containing Random Access MemoryChips (the electronic devices that store data while your computer works with it). SIMMs plug into special slots inside the computer to give the computer extra memory.

special effects:

Digital image manipulation techniques for enhancing quality or creating unusual appearances. Can also be used to remove undesirable image attributes.

spray:

To paint with a diffused edge to simulate "air-brush" feathering

storyboard:

A method of planning the content of a presentation by drawing sketches of each screen with notes about what happens in that scene.

substitution:

the process of replacing colors in a image with colors or patterns on the pallet for the image. this is implemented during color format conversion and pallet correction

Syquest:

A manufacturer of SCSI removable cartridge hard drives. this drive specification has been widely used in pre-press and publishing situations.

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tablet:

A pressure sensitive input device used in conjunction with a pen to edit digital images.

touch-screen:

A display monitor that is pressure sensitive to touch and is often used as a multimedia control instead or in conjunction with a keyboard. Better authoring systems should have touch-screen interface functions built in their software. Touch-screen displays vary widely and can be accomplished with special overlays or can come as integral screens with built-in touch-screen capabilities. The best screens also feature z-axis control, which allows screen response at different rates depending on the level of pressure applied.

track:

A sequence of contiguous data, the beginning, length, mode and end of which are defined in the table of contents, which is held in the Q subcode channel of the lead-in area of the disc. The two types of tracks currently defined are the CD-DA track according to the CD-ROM specification that is also used in CD-I. In CD-DA the length of a track is related to playing times between four seconds and 72 minutes.

tuning:

The Group term for a number of image editing activities including color and grey balancing, hue & saturation, gamma, histogram, and contrast adjusting...etc.

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U...

UU

u

UART:

Universal Asynchronous Receiver-Transmitter. An electronic circuit contained within the communications port(s) of the computer that decodes and encodes data in the fashion required by the specific machine for receiving and transmitting purposes. The UART also performs the actual data transmission to the communication device, once it has been encoded and is ready to send.

UPS:

Uninterruptible Power Supply. A battery reserve system for computer power installed to supply power in the event of outage. These systems protect against data loss during power outage.

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V...

video capture:

The term for converting analog video signal to digital stills and Motion files.

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warp:

A special effect sequence of morph images that simulate smooth transitions of dissimilar frames.

WYSBYGI:

"What You See Before You Get it." An extension of WYSIWYG interface design allowing the user to view and edit selected smaller areas from a preview dialog box prior to committing special effects with the processing load of only a portion of the entire file.

WYSIWYG:

"What You See Is What You Get." A working interface of many authoring systems where an author sees the screens as he develops them exactly as they will appear to the user.

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X...

XX

x

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Y...

YY

y

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Z...

ZZ

z