DataRecoveryUnion.com

EIDE (Enhanced Integrated Drive Electronics)
The primary interface used by desktop PCs to handle communication between hard drives and the central processing unit. The equivalent interface system in most enterprise systems is SCSI.

Embedded Servo Control
The embedded servo control design generates accurate feedback information to the head position servo system without requiring a full data surface (which is required with a “dedicated” servo control method) because servo control data is stored on every surface.

Encoding
The process of modifying data patterns prior to writing them on the disk surface.

Enterprise
The series of computers employed largely in high-volume and multi-user environments such as servers or networking applications; may include single-user workstations required in demanding design, engineering and audio/visual applications.

Error Correction Code (ECC)
A mathematical algorithm that detects and corrects errors in a data field.

Error Log
A record that contains error information.

Error Rate
The number of errors of a given type that occur when reading a specified number of bits.

Extended Partition
You can create multiple partitions on a hard disk, one primary partition and one or more extended partition(s). Operating system files must reside on the primary partition. An extended partition is a partition where non-system files (files other than DOS or operating system files) can be stored on a disk. You can also create logical drives on the extended partition.

Database
A collection of data stored on a computer system medium, such as a hard drive, CD-ROM, etc., that can be used for more than one purpose.

Data Recovery
Data recovery is the procedure used to recover data from a variety of media and operating systems that has been lost by either hardware failure, human error, software bugs, a virus or a natural disaster.

Data Synchronizer
An electronic circuit that uses a clock signal to synchronize data to facilitate interpretation.

Data Transfer Rate
The rate that digital data transfers from one point to another, expressed in bits per second or bytes per second. Data Transfer Rate to Disk: The internal disk transfer rate in Mbits per second.Data Transfer Rate from the Buffer to the Host: Based on the transfer of buffered data in MB per second.

Dedicated Landing Zone
The designated radial zone of the disk, usually at the inner portion of the disk, where the heads are stored to avoid contact with the data cylinders when power to the drive is off.

Defect Free
A term used to describe recording surfaces that have no detectable defects.

Defect Management
A general methodology of eliminating data errors on a recording surface by mapping out known defects on the media. The defective areas are rendered inaccessible, so that when information is written to the disk, it is stored to non-defective locations on the disk.

Differential SCSI
An electrical signal configuration which uses pairs of lines for data transfer. Used primarily in applications requiring long cable lengths of up to 82 feet (25 meters).

Direct Memory Access (DMA)
A process for transferring data directly to and from main memory, without passing through the CPU. DMA improves speed and efficiency by allowing the system to continue CPU processing even while it is transferring data to/from the hard drive.

Directory
A list of file names and locations of files on a disk.

Disk
A rigid platter, usually constructed of aluminum or mylar, with a magnetic surface that allows the recording of data, that is stored inside the drive.

Disk
A portion of a computer’s RAM set aside for temporarily holding information that has been read from a disk. The disk cache does not hold entire files as does a RAM disk, but information that has either been recently requested from a disk or has previously been written to a disk.

Disk Controller
The chip or circuit that controls the transfer of data between the disk and buffer. (See also disk drive controller and interface controller).

Disk Drive
The motor that actually rotates the disk, plus the read/write heads and mechanisms.

Disk Drive Controller
The hard disk drive controller electronics which include the disk controller and the interface controller. (See also disk controller and interface controller.)

Disk Operating System (DOS)
The computer program that controls the organization of data, files and processes on the computer.

Disk Transfer Rate
Speed at which data transfers to and from the disk media (actual disk platter); a function of the recording frequency. Typical units are bits per second (BPS), or bytes per second. Hard drives have an increasing range of disk transfer rates from the inner diameter to the outer diameter of the disk.

Distribution Channel
Electronics distributors and certain retail chains that deliver electronic goods to end users through value-added resellers and some retail stores.

CMOS Setup
A program supplied in most systems that allows you to configure internal and external devices.

Cable Select (CSEL)
An alternative option which can be used in place of setting Master/Slave jumpers in the designation of drives in a dual drive configuration. Master/Slave designation is based on the position of the drives relative to the cable. Special cabling is required by the system manufacturer to selectively ground the CSEL signal on one of the IDE cable connectors. For example, when one of the drives is connected to the grounded CSEL conductor, it configures itself as the Master. When the second drive is connected to the other connector, on which CSEL is not grounded, it becomes the slave. This eliminates the need for unique jumpering configurations between the Master and Slave drives.

Cache
High-speed RAM used as a buffer between the CPU and a hard drive. The cache retains recently accessed information to speed up subsequent accesses to the same data. When data is read from or written to disk, a copy is saved in the cache, along with the associated disk address. The cache monitors the addresses of subsequent read operations to see if the required data is already in the cache. If it is, the drive returns the data immediately. If it is not in the cache, then it is fetched from the disk and saved in the cache.

Capacity
The amount of information, measured in bytes, that can be stored on a hard drive. Also known as storage capacity.

Central Processing Unit (CPU)
The main processing chip of a computer. The CPU interprets and executes the actual computing tasks, and has the ability to transfer information to and from other resources over the computer’s main data-transfer path, the bus.

Channel
A connection or socket on the motherboard or controller card. A motherboard may have one or two channels (primary and secondary). If your motherboard has only one channel, you may need to add a controller card to create a secondary channel.

Channel Assembly
In the computer industry, the final assembly of a system by a distributor or reseller from kits provided by the manufacturer and from components shipped directly to the assembler by subsystem makers.

Clean Room
An environmentally controlled, dust-free, assembly or repair facility in which hard drives are assembled or opened for internal servicing.

Cluster
A hard disk term that refers to a group of sectors. A cluster is considered an allocation unit. At least one cluster is allocated to each file, regardless of the file’s size, that is stored in the DOS environment. The cluster size increases with the partition size determined during formatting. With a 1024 MB partition, the cluster size is 32 KB. Each file stored consumes 32 KB of storage space, no matter how small the file. Create multiple, smaller partitions to avoid wasting space on small files. (This definition applies to FAT16).

Command Aging
A SCSI feature that prevents the command reordering algorithm from keeping I/O processes waiting in the command queue for extended periods of time.

Command Queuing
A feature that enables the drive to receive I/O processes from one or more initiators and execute them in an optimum sequence.

Command Reordering
A feature that allows the drive to reorder I/O processes in the command queue, which results in minimizing the seek time and rotational latency and thus increases throughput.

Controller
A device that transfers information between the computer and peripheral devices. The controller (or “control unit”) acts as a traffic manager. See also disk controller, interface controller, and disk drive controller.

Controller Card
An adapter with the control electronics for one or more hard drives. Usually installed in a bus slot in the computer.

Correctable Error
An error that the drive can correct by using Error Detection and Correction schemes.

Customer Configuration Code (CCC)
A firmware revision tracking code that defines a major product change. This number increments as form, fit or function changes are implemented. The CCC code guarantees that the correct revision of drive product is provided to the customer.

Cyclic Redundancy Check (CRC)
Data stored or transmitted with data to detect corruption. By calculating the CRC data and comparing it to the original data sent, the receiver can detect some types of transmission errors.

Cylinder
The cylindrical surface formed by identical track numbers on vertically stacked disks.

Cylinder, Head, Sector (CHS) Addressing
A method of referencing the sectors on a drive as a collection of unique cylinder, head and sector addresses. Each block on the drive will have a unique cylinder, head and sector address.