2024-11-29

Data Recovery Glossary (Letter A)

DATARECOVERYUNION.COM05 mins

AFR
Annualized Failure Rate.

ATA (Advanced Technology Attachment)
A disk drive interface standard for IDE (Integrated Drive Electronics). A standard for storage devices that lets them be treated as if they were hard drives on the system. Any ATA compatible media can be read by any ATA device.

Access
Retrieval of data from or transfer of data into a storage device or area such as RAM or a register.

Access Time
The amount of time, including seek time, latency and controller time, needed for a storage device to retrieve information.

Active Partition
The partition of the drive that contains the operating system. If the drive has multiple partitions, only the primary partition can be made active. A hard drive can have only one active partition.

Active Termination
One or more voltage regulators that produce termination voltage. The voltage regulator(s) drive a constant voltage along the bus to ensure that the data signal stays constant and strong over the entire length of the bus. The result is increased data integrity and reliability.

Actuator
A mechanical assembly that positions the read/write head over the appropriate track.

Actuator Arm
The part of the actuator assembly that includes the positioning arm and the read/write heads.

Adaptive Caching
A feature of hard disk drives that enables them to improve performance and throughput by adapting to the application being run.

Address
In the hard drive industry, there are several types of addresses; an address may refer to that of a drive, called a unit address; radial position, called a cylinder address; or circumferential position, referred to as a sector address.

Allocation
The method DOS uses to assign a specific area of the hard drive to a given file. (See also cluster.)

American National Standards Institute (ANSI)
A governmental body of the United States responsible for approving US standards in many areas, including computers and communications. ANSI is a member of the International Standards Organization (ISO).

Arbitrated Loop
Fibre channel topology where two or more ports can interconnect but only two ports can communicate at the same time.

Arbitration
The act of determining which command, device, or communication protocol controls the operating environment.

Areal Density
The number of bits of data that can be recorded onto the surface of a disk or platter usually measured in square inches. The areal density is calculated by multiplying the bit density (BPI – Bits Per Inch) by the track density (TPI – Tracks Per Inch).

Asynchronous Transmission
Each byte of information is synchronized individually through the use of request and acknowledge signals.

AT Bus Attachment (ATA-4)
The interface defined by IBM for the original AT disk controller.

Auto Defect Retirement
If the drive finds defective sectors during reads or writes, they are automatically mapped out and relocated.

Auto Park
Turning off the drive power causes the drive to move the read/write heads to a safe non-data landing zone and lock them in place.

Average Access Time
The average length of time a drive takes to perform seeks, usually measured with 1/3 stroke.

Average Seek Time
Length of time it takes the drive to move the read/write heads to a safe non-data landing zone and lock them in place.

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Top 10 Data Disasters Stories for 2011 (Kroll Ontrack)

DATARECOVERYUNION.COM07 mins

Think you have the worst data disaster story? Let’s find out! Submit your top data disaster for the chance to win an iPad2. – Ontrackdatarecovery.co.uk

data-disasters-2011

Top 10 Data Disasters Stories for 2011:

1. Triple whammy
When a lightning strike caused a fire that sent a famous Caribbean island home up in smoke, the computer servers were burned and then doused with water by the firemen. The media then corroded while the building sat idle until it was safe to re-enter. In the end, the triple whammy of a lightning strike, fire and water damage was overcome in the Ontrack Data Recovery cleanroom.

2. Doggy eat dog world
A man encouraged his girlfriend to back up her photo library, which contained thousands of high-resolution photos from her photo studio. She diligently moved the data from her laptop to an external hard drive, but unfortunately that represented the only good copy. A friend then pulled into the driveway and the couple went out to meet her, but not before the hyperactive family dog heard someone at the door and came tearing out from underneath the table where the drive was sitting. The drive went crashing to the floor, causing much damage to the data.

3. A little piece of history
A freelance photographer happened to have his camera with him in the midst of the recent London riots. Some rioters saw they were being filmed and opted to smash the camera in order to destroy the potentially incriminating evidence. The camera made its way to Kroll Ontrack where 100 percent of the data and the video footage was recovered and supplied to the police.

4. In the safe not on the safe
To avoid arriving late to a business meeting, an IT person opted to put a tape drive on top of the waterproof safe instead of inside it. Within an hour of doing so, the city was struck by a powerful earthquake and the tape was knocked to the ground. Then, the premise was engulfed by mud, water and sand. The tape looked irrecoverable.

5. Smoking kills
A newly hired security guard was doing his first evening security check in a chemical ingredients warehouse. While he was informed that smoking is forbidden, he pondered who could possibly spot him enjoying a cigarette after company hours. After it was lit, the fire alarm sounded and prompted the anti-fire sprinkler system. All the electronic equipment, including 44 desktops and two servers, were flooded.

6. Sunken business deal
Two businessmen met in a pub to discuss a future deal over a beer. The waitress accidently knocked over one of the glasses she was delivering, soaking the laptop which contained the business plans. A paper towel was not enough to save the laptop and its important deal files.

7. End of month disaster
A corporate accounting department stayed late to reconcile the books for the month. While rejuvenating on a coffee break, a power outage occurred. All of the computers shut down including the financial server. Luckily the department’s computers were connected to a UPS. However, the continued brewing of their cups of Java drained the UPS battery, resulting in a crashed server.

8. Magnetic attraction
A laptop was set down on a desk near some rare earth magnets. The earth magnets came into contact with the laptop and when the user went to turn on the machine, it did not fully boot up and started clicking. Physical damage was caused to the platters.

9. Virtual reality
To increase system performance, an IT administrator split the C and D partition of his virtual server across two different systems. Running out of space, the admin needed to rush and consolidate C and D onto the same system. Not knowing that the same naming convention already existed on the target system, he copied over the important data set.

10. Bad image
An actor deleted her entire portfolio including her model card samples and recent pictures by accidently selecting the wrong externally attached USB drive using the MAC disk utility program.

Note: Submit your worst data disaster story by January 31, 2012. Include how the data disaster occurred, how it impacted you or your business and if you were able to recover your data (if so, how much you recovered). The winner will be selected on February 1, 2012. Join Now

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What if the Flash Device Is Damaged?

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Data Recovery is always an option for these types of devices. The quality of the recovery depends on how much usable data there is. In the British television program mentioned earlier, after the flash drive was shot out of the cannon and damaged, the producers sent the damaged flash device it to professional data recovery company After working with the device and its pieces, the engineers were able to recover the data on the device and found the data the producers were expecting.

Never assume that the data is gone when physical damage has occurred. The experienced data recovery engineers are capable of repairing complex electronics on USB flash drives.

What about deleted or reformatted USB flash drives? Similar to hard disks, when a USB flash drive is reformatted or data is deleted, the file system addresses to the data are erased—not the data itself. Even if some files are re-saved back to the device, there may be a chance that the information is recoverable. In simple deleted recovery situations, do-it-yourself solutions by using the professional software would be able to find the data and bring it back. In more complex situations where data has been restored back to the device, a trained data recovery engineer would be able to tell the difference between the newly written data and the original data. After an evaluation, the user would know exactly which files sustained damaged and which ones did not.

As long as the flash media is not physically damaged, a quick recovery choice for USB flash drives is that chooses the Remote Data Recovery service from professional data recovery company. The remote engineers can work on your flash drive while it’s still plugged into your computer and has access to the internet or to a modem.

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Terminating the SCSI Bus

DATARECOVERYUNION.COM06 mins

Terminating The SCSI Bus What is Termination?

Cables make up the physical connections of the SCSI bus. Since the SCSI bus is a chain of devices on a cable rather than a loop, the two ends of the bus must be terminated. Every wire in the cable has a specific impedance, or resistance to the passing of electrical signals. When signals reach the end of the cable that makes up the SCSI bus, they encounter the air, which has very high impedance and acts as a wall of infinite resistance. The problem with high impedance is that any signal coming down the bus is reflected back in the other direction once it hits this barrier. Terminating both ends of the cable prevents the signal from being reflected.
You terminate the bus by attaching a circuit, the terminator, to the physical ends of the SCSI bus. The terminator provides an impedance that matches the cable’s, thereby preventing the signal from bouncing back. The terminators use power, and the power to operate them comes from the SCSI interface card through the termination power wire on the bus.

What is Passive Termination?

Passive Termination is the oldest method of termination, defined in the specs for SCSI-1. Basically, a passive terminator sits on the bus to minimize reflections at the end of the cable. The terminator doesn’t really do any work to regulate power for termination; it relies on the interface card to provide steady power. A passive terminator simply provides impedance that’s close to the impedance of the cable.

What is Active Termination?

Active termination works to control the impedance at the end of the SCSI bus by using a voltage regulator, not just the power supplied by the interface card. Because it is active, regulating the power that it gets from the interface card, active termination is more stable than passive termination.

What is Forced Perfect Termination (FPT)?

Forced perfect termination is the most complex of the terminators, going beyond merely stabilizing the power applied to the terminator. It can actually alter its impedance to compensate for variations in impedance among many different cables, devices, and terminators. It is usually used in high-speed SCSI systems that have many different devices, cables, and terminator types. The complexity of such a system can cause impedance mismatches that degrade the signals sent through the bus. FPT actively compensates for these impedance variations by means of diode switching and biasing to force the impedance of the cable to match each device.

How do I terminate Seagate SCSI disc drive?

If you are installing a Seagate drive in a system that has other SCSI devices installed, terminate only the end devices on the SCSI chain. A SCSI “device” is any disc drive, scanner, tape backup unit, or other piece of hardware connected to your system using the SCSI bus.

Terminating The SCSI BUS

The example above shows an internal hard disc at one end of the SCSI bus with the SCSI controller at the other end (both are terminated). The bottom example shows two additional SCSI devices connected externally-this means the SCSI controller is no longer on the end of the SCSI chain and should not be terminated.

Note: Some controllers prefer to remain terminated even if they are in the middle of the chain. Also, some controllers treat the internal and external chains as separate logical buses. This means you may need to terminate both the first and last devices on both logical buses to achieve proper termination. If necessary, refer to your system or controller documentation to see how this is handled in your particular system.

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