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Data Recovery Glossary

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Access: To locate the needed data.
Access Time: The time interval between when data is called for or requested to be stored in a storage device and when delivery or storage is completed.
Accidental format: Reformatting the disk by mistake. The important data was not backed up.
Actuator: The device that moves the read/write heads across the platter surfaces.
ATA: Advanced Technology Attachment, the more correct name for the IDE interface used for connecting the storage devices like hard drives and CD-ROM drives inside personal computer. There are multiple levels of ATA standards: ATA-1(IDE), ATA-2(EIDE), ATA-3, ATA/ATAPI-4(Ultra ATA/33), ATA/ATAPI-5(Ultra ATA/66), ATA/ATAPI-6(Ultra ATA/100), ATA/ATAPI-7(Ultra ATA/133), ATA/ATAPI-8.
ATAPI: Advanced Technology Attachment Packet Interface for devices like tape drives, zip drives and CD-ROM.
Average seek time: The average time a disk drive takes to locate a specific track and sector. It refers to the time taken by a read/write head to move to a specific location.


Backup: The copying of contents of all or part of a storage device, usually from internal device, onto an external device.
Backup file: A duplicate copy of a file.
Backup failure: Backup has a tendency to fail the same way as an original data. The reason is instability of data storage such us media failure, human error and hardware malfunction.
Bad Sector (Bad Block): A disk sector that cannot be reliably used for storing and retrieving data due to media damage.
BIOS (Basic I/O system): A set of routines that works closely with the hardware to support the transfer of information between elements of the system, such as memory, disks, and monitor.
BIOS errors: BIOS runs a diagnostic test each time the computer boots up checking all the hardware workability. Any errors detected are reported via audio beeps or messages. When experiencing problems with the hard disk drive in the system, you probably can see the error messages such us "Non-System disk or disk error", "Disk Boot Error", "Hard Disk Failure", "Hard Disk Controller Failure", "HDD Controller Failure".
Bit: The smallest unit of information handled by computer. Bit represents 1 or 0 in a binary numerical, a true or false. A group of 8 bits make a byte.
Bit Density: Expressed as "BPI" (bits per inch), bit density defines haw many bits can be written onto one inch of a track on a disk surface.
Block (Sector): A unit of the storage media whose size is determined at the time of high-level formatting.
Boot: To start up the computer or operating system.
Boot drive: The disk drive from which the operating system was booted.
Boot sector: First sector on a logical drive that includes code to boot that drive, specific logical drive information, and error messages.
Buffer: Temporary storage used to compensate for a difference in rate of flow of data, or time of occurrence of events, when transmitting data from one device to another.
Buffer overflow: Occurs when a program tries to store more data into the buffer than it can actually hold. Buffer overflow may result in a system crash or even loss or corruption of data. When excess information is tried to store in the buffer, the extra information goes to the adjacent buffer and cause data corruption and overwriting.
Burned power supply: A power supply (PSU) provides electricity to every component of a computer, so it's burning will often cause hard drive failure or other electronic components due to voltage problems, sudden power spikes, or power supply overheating.
Bus: A set of hardwire lines used for data transfer among the components of a computer system.
Byte: A set of 8 binary digits.


Cache: Caching is a method of increasing performance by keeping of frequently used data in a location which is more quickly accessed.
Cache memory: A high-speed temporary storage area in the CPU for storing parts of a program of data during processing.
Capacity: The total space in megabytes available on the hard disk.
Clean Room: Environmentally controlled area for repair facility in which hard drives are opened for internal servicing or repair. A clean room has to be dust free and bacteria free to avoid any further damage to the hard drives during servicing.
Clicking noise: Generally, clicking sound coming from the hard drive indicates that hard drive is suffering from physical damage such us head crash, bad sectors, and mechanical failures. When you hear clicking sound it might be too late to make backup.
Controller: The printed circuit board (PCB) required to interpret data access commands from host computer (via the bus), and send track seeking, read/write, and other control signals to and from a hard drive.
Corrupted data: Changed or damaged data somehow that it can no longer be used and accessed. The most common reasons for data corruption are shocking system shutdown, disk failure, hardware failure, and over-written data to become unreadable.
Corrupted Drive: There are different causes of hard drive corruption: sudden disastrous failure, head crash, pollution of the air inside the drive unit, general surface wear, and bad sectors.
CPU: Central Processing Unit.
Crash: A hardware or software failure that leads to an unexpected stop of a program.
Cryptography: Conversion of data into a secret code for protection of privacy using a specific algorithm and a secret key. Cryptography is used to protect email messages, credit card information and corporate data.
Cylinder: The set of concentric tracks of data located at the same position on each data- bearing surface of the disk.


Damaged file: File that gets damaged, becomes unreadable, and won't be accessed due to hard drive malfunction, human error, and virus attack.
Data Transfer Rate (DTR): Speed at which bits are sent. In a disk storage system, the communication is between CPU and controller and the disk drive.
Data Recovery: The process of recovering the lost and inaccessible data from the damaged storage media. Data may be lost due to hard drive crash, system failure, virus attack, software failure and natural disasters.
Dedicated Servo System: A complete disk surface and head are dedicated for servo data.
Direct Memory Access (DMA): A method whereby peripherals may transfer data into or out of main memory without the involvement of the CPU.
Disk: A storage device or media used for storing digital or computer information.
Disk Platter: A flat, circular disk substrate coated on both sides a magnetic substance for non-volatile data storage. The substrate may consist of metal, plastic or glass.
Drive deterioration: The most common cause of a faulty hard drive is mechanical wear and tear and the deterioration of components over time. Head crash and bad sectors can result of permanent data corruption. With S.M.A.R.T. or other hard ware diagnostic tests it is possible to check the hard disk performance and prevent an impending failure.
Dropped disk: Accidentally dropped data storage device can be caused data loss on it. Such a disaster can result head crash, head sticking, firmware corruption, circuit board damage.


Electrical failure: Electrical components of hard drive are damaged due to faulty components, electro-static discharge, contamination, corrosion, and thermal stress and caused of losing access to the data. The drive isn't recognized by BIOS, and won't spin when the computer is powered up.
Embedded Servo System: the method of using the space between sectors of a hard drive to provide servo-positioning information. Servo data is embedded along with data on every cylinder opposed to having a dedicated servo track.
EIDE: Enhanced Integrated Drive Electronics. It acts as a standard interface between a computer and its storage devices. EDIE is a hardware interface and faster than the IDE. It allows for high performance and large capacity drives.
Encryption: A way of making data impossible to read to protect it from unauthorized viewing or use.


FAT file system: A file system based on a file allocation table, maintained by the operating system, to keep track of the status of various segments of disk space used for file storage.
FAT corruption: Usually a boot sector might be corrupted due to hardware failure or virus infection.
File: A collection of related data records treated as a unit.
File Allocation Table: FAT is a table maintained by the operating system to keep a track about the disk space (clusters) utilized by the files and the disk space available for future allocation.
Firmware: Firmware is the software embedded in the computer hardware devices instructing how to perform and execute. Some of the examples of firmware are BIOS found in PC's, ACRS used for silicon graphics, and Open Firmware used in Apple computers.
Formatting: Preparing a data storage for storing data. Low-level or physical formatting writes all necessary data to enable the storage device to read the media and initialize the storage units on the media to a known state. High-level or logical formatting writes data used by the operating system, such as allocation information and directories onto media, which has already been physically formatted. Formatting program usually performs both a low-level and high-level formats.


Gigabyte: A unit of measuring the computer data storage capacity. A gigabyte consists of one billion bytes or 1024 megabytes.


Hard Disk: A magnetic round platter (platters) coated with magnetizable substance.
Hard Disk Drive: The device used to transfer data to and from a hard disk.
Hard drive crash: Failed hard drive. The symptoms of hard disk crash: computer will not boot, blue or black screen, clicking noise from the drive, rebooting, restarting, or freezing of system.
Head: There are usually several read/write heads in a hard drive. The term "heads" only pertains to actual data heads, those that read/write, that means only one of the several read/write heads is in use at any one time.
Head Crash: A catastrophic failure that causes permanent damage and data loss. As a normal operation, head landing occurs when the disk drive is turned off. When the heads land, a thin film of lubricant on the disk surface protects the disk from damage. Ahead crash occurs when the head and disk damage each other during landing because of rough handling.
Head Parking: Parking the heads places them in a safe zone away from data on the platter, usually the highest cylinder on the drive.
Human error: The most prevalent cause of data loss is accidental or unknowing data deletion, modification, and overwrites. User tech-education and limiting permission for accessing the critical data is probably the most important factor of preventing loss of vital data.


Interface: Interface is a software or hardware protocol that facilitates communication between hardware device, applications or different sections of a computer network. Some of the common interfaces are AT (IDE), SCSI and GUI of Microsoft Windows.
Inaccessible Partition (Corrupted Partition): The first sector of disk stores a special data structure called the Master Boot Record, which composed of two parts -the master boot code and the partition table. A damaged Master Boot Record or corrupted partition table will always result in loss of access to entire partitions or even the entire hard disk. Also, accidental partition deletion will make all data in the deleted partition inaccessible.
IDE: Integrated Drive Electronics. Also known as ATA interface. IDE is a hard drive interface used between computer's data paths and the storage devices. It is a method for connecting the hard disk with the computer. IDE is integrated into the motherboard of a computer and allows a connection of only 2 devices per channel.
Index Pulse: The starting point for each disk track. The index pulse provides initial synchronization for sector addressing on each individual track.


Landing Zone: The section of the disk that is designed as the safe zone for head parking. See Head Parking.
Lost files: Files that have been lost or deleted due to the hard drive formatting or crash, virus attack, accident system shutdown, or software malfunction.
Lost Partition (Missing Partition): The partition table or boot sector of partition is destroyed due to accidental deletion, or formatting, or virus attack.


Megabyte: One million bytes.
Media Corruption (Media Failure): The inability to access the data on a digital storage devices due to general wear and tear of the media, environmental threats such as power outages, dust, water, and extreme temperatures.
MTBF: Mean Time Between Failures. This figure is supposed to indicate how long a drive is expected to last.
Mechanical Hard Drive Failure: Includes component failures related to the mechanics of the disk: damage of the spindle motor, head crashes (clicking or grinding noises from the hard drive), actuator problems.


No spin: The drive won't spin. The basic problem is a sticking of the read/write heads to the platters inside, and the motor is disabled to get started spinning. The circuit board problem can be cause of no spin.
Noisy hard drive: A hard disk drive making a grinding or constant clicking noise can usually be considered failed.
Not Recognized Drive: or no hard drive found is a message sometimes coming when booting up. There are several possibilities why a hard drive may not be recognized such us incorrect hard drive settings, system virus, data corruption, hard drive configuration.
NTFS corruption: The common NTFS-related problem involves a corrupt boot sector, which can cause boot problems, or even worse, can make the data on the volume inaccessible.


OEM: Original Equipment Manufacturer that is installed in the machine by the vendor.
Operating System (OS): A set of programs that controls and supervises a computer system's hardware and provides services to programmers and users. Some examples of operating system are Windows NT/XP, 2000, Linux, UNIX, Macintosh etc.
OS upgrade: The upgrade normally includes many new and improved features. For some reason users forget to back up the data before installation of new OS version and lose it by overwriting.


Partitioning: Partitioning divides a physical hard drive into logical volumes. Partitioning is the act of dividing a disk into isolated sections; each section is treated as a separate disk drive. Partitioning is useful if running more than one operating system.
Platter: The circular aluminium or other surface where the actual data stored. A disk drive contains several platters and each platter requires two read/write heads for accessing the data. A single scratch on the platter can cause data loss.
Power spike: Fast ,short electrical jumps. There are voltage spikes, current spikes or energy spikes in an electrical circuit. Data storage equipment damages from spikes if not prevented by surge protector.
Power Surge (Outage): Also known as power failure is the loss of the electricity supply. Hard drives are extremely vulnerable to power failure.


Random Access Memory (RAM): A storage device structured so that the time required retrieving data is not significantly affected by the physical location of the data.
RAID: Redundant Array of Inexpensive Disks. Relatively inexpensive way to increase capacity and/or reliability in mass storage. One of the most important features is the ability to guard data against media failure by simultaneously duplicating all information.
Repartition: When user want to install a second Operating System on computer the common task is to repartition the hard drive. Another hard disk repartitioning advantage is separation of programs and data. To avoid losing data do backup onto the second drive before repartitioning.
Rotational Speed: The speed at which the media spins.


SCSI: Small Computer System Interface used to connect hard drives and other computer peripherals like tape drives, CD players, scanners etc. SCSI is an extremely fast device access protocol that transmits data at a high speed of 80 megabytes per second.
Sector (Block): A hard disk is divided into various sections to conveniently store data. A section of one track is called a sector. Each sector is defined with magnetic marking and an identification number. One sector of a disk stores one record, which is usually 512 bytes.
Sector Header: The address portion of a header. It includes the cylinder, head, and sector number of current sector.
Seek: The radial movement of the heads to a specified track address.
Seek Time: Usually refers to the average time it takes the heads to move from one track to another, on average.
S.M.A.R.T. failure: S.M.A.R.T. system provides an early warning for many types of potential problems of the hard disk drives. If you receive a message that " SMART Failure Predicted on Hard Disk ", it means that your hard drive will fail most likely soon. Make a backup copy of your important data from the failing drive immediately.
Spindle: The rotating hub structure to which the disks are attached to rotate at high speed to facilitate read/write actions to be performed.
Spindle Motor: This is the motor that spins the platters.
Spilled Water/Coffee/Liquid: Accidents with beverages such us water, coffee, bear, wine spilled while working on laptops can cause an extremely damage of laptop data storage and data loss, too. Spilled liquid, especially sweetened, can stick hard drive platters or spindle motor. The computer shuts down applications without warning, or restarts, or freezes, or stays at blue screen.


Track: The concentric circles that hold data on a disk platter. A track is composed of a circle of magnetic flux changes. Each track is divided into sectors.
Track Density: Track density or track per inch defines how many tracks can be written onto a disk surface.


Unbootable System: Two scenarios: the operating system simply won't run, BIOS setup program displays the "non-system disk" or "missing operating system" message; the operating system starts booting, but after some time it freezes or the boot process is interrupted by an error message.


Voice-Coil Actuator: The head actuator is responsible for moving the heads back and forth over the platters. Voice-coil actuators use a solenoid to pull the heads toward the centre of the platter.