Hard Disk Glossary of Technical Terms

This page includes a comprehensive list of terms related to hard drives. It defines the meaning of many technical terms used by hard drive recovery specialists when they talk about hard drives and digital storage devices.

A-cable

Term used to describe a standard SCSI Cable.

Access arm

Also known as a head arm or actuator arm, the access arm is similar to an arm on a record player and is found inside all computer hard disk drives. The access arm allows the hard drive to move the read/write heads to the locations where information needs to be read or written to. Below is a basic illustration of the inside of a hard disk drive as well as an example of the access arm.

Access light

Also known as the activity light, the access light is a LED on the front of a computer and/or disk drive that indicates when the computer or disk drive is being used.

Actuator

An actuator is an electronic device controlled by a motor that moves the head arm to where it needs to go. In the past the actuator within a hard disk drive was controlled by a stepper motor. However, today the actuator is commonly controlled by a servo motor.

ADSM

Short for ADSTAR Distributed Storage Management, ADSM is IBM’s software that helps clients manage storage devices.

Allocation unit

Group of reserved sectors on a computer hard disk drive.When referring to memory, an allocation is a process preformed by the computer that assigns a block of memory for a program to store its data or information in.

Anti vibration mount

Drive bay mount that locks the hard drive or other 3.5-inch device in one place so that the read/write heads and other mechanisms are protected from movement.

ATAPI

Short for AT Attachment Packet Interface, ATAPI is an extension to ATA which allows support for devices such as CD-ROM drives, Tape drives and other computer peripherals and not just hard disk drives. Before the release of ATA-4 or ATAPI-4, ATAPI was a separate standard from ATA.

BIT

Sometimes abbreviated as b, a bit is short for Binary digIT and is a single unit of information that can have a value of either ON or OFF.

Bad sector

Refers to a flaw with the hard disk drive disk or a manufacturer defect. When bad sectors are encountered it is generally a defective disk or hard disk drive and it will need to be replaced.

Block

When referring to a hard disk drive or other storage medium, a block is a segment of a large area that can be assigned to store data.

Partition

When referring to a computer hard disk drive, a partition is a segment of the hard drive that is separated from other portions of the hard disk drive. Partitions help enable users easily divide a computer hard disk drive into different drives and/or into different portions for multiple operating systems to run on the same drive. With older file allocation tables, such as FAT16, creating smaller partitions allows a computer hard disk drive to run more efficiently and save more disk space. However, with new file allocation tables, such as FAT32, this is no longer the case.There are various types of utilities used to create and manage partitions on hard disk drives, one of the most commonly used and known utilities is Microsoft fdisk.

BPB

Short for BIOS Pattern Block, BPB is the first section of the boot sector that defines the settings and layout of a hard disk drive’s partitions.

Bus mastering

Also sometimes referred to as BSIDE (Bus Mastering Integrated Drive Electronics) on IDE, bus mastering is a method of transferring data without having to use the CPU.

Byte

Byte is data equal to either 7/8 bits depending if it needs error correction (parity).  A byte is spelled as byte and not bite.

Cable select

Often abbreviated as CS, cable select is a disk drive setting that will allow a cable select compatible cable to determine what drive is the master and slave based off where the drives are connected to the cable. For cable select to work the both IDE / EIDE drives must have their jumpers set to CS and be connected to a cable that supports cable select.Users can easily identify if the flat ribbon cable supports cable select by examining the cable for any of the below characteristics. Cable is an 80-connector UltraATA cable. Cable has master and slave printed on the cable or on the cable connectors.

Capacity

The maximum amount of data that a device such as a hard drive can hold. If and when the device reaches its capacity it will no longer be able to hold more information.

Cluster

When referring to a hard disk drive, a cluster is a managed section by the computer’s Operating System that changes size depending upon the size of the hard disk drive. Because each file and even directories take up one or more clusters depending on their size, earlier types of FAT potentially wasted hard disk drive space. For example, if the cluster size was 8k and a 2k file is stored on the computer, 6k of that cluster will go to waste. This issue has been reduced with new versions of FAT have been made available such as FAT32 that help resolve this issue.

Contiguous

In general, refers to an object that is adjacent to another object. When referring to a computer hard disk drive, contiguous means sectors on a disk that are by each other. When referring to computer memory, contiguous means sections of memory that are next to one another.

Cylinder

Two corresponding tracks on a fixed disk.

Daisy Chain

A number of hardware devices that are connected together with cables that resemble a chain. Generally, a SCSI device or devices are daisy chained; this allows for multiple devices to work off of one card.

DASD

Short for Direct Access Storage Device, DASD is used as another name for a disk drive.

Data buffer

An alternate, generally temporary, location to store data while being moved from one location to another.

DDO

Short for Disk Drive Overlay, DDO is a TSR that loads onto sector two of the hard drive and is used for computers that do not support LBA mode. DDO allows the computer to support and see larger than 520 MB.

Deceleration Time

Term used to describe the amount of time for the hard drive head to slowdown as it moves to a portion of the disk to retrieve information.

Defragmentation

Term used to describe the process of reorganizing a hard disk drive’s data to help increase the proficiency of accessing the data. Hard disk drives that are severely fragmented will take longer to access the data because it is spread across the drive and not located in a central area.

Direct access

Sometimes known as machine access or random access, direct access is a term used to describe the ability of a computer to locate and retrieve data immediately from a storage device without having to start at the beginning and read all information until the requested data is found. For example, a hard disk drive is capable of directly accessing data. However, a tape drive must access all information before the requested data is retrieved.

Disk

Hard or floppy round flat magnetic data storage platter that is capable of having information saved to it. It is more appropriate to refer to a floppy disk as a floppy diskette.

Disk access time

The total time required for the computer to process the data request from the processor and then retrieve the required data from a storage device.

Disk capacity

The complete number of bytes that a disk drive is capable of holding.

Disk controller

Printed circuitry that contains the necessary instructions of diskette drives. The disk controller is responsible for such drives as the hard disk drive, floppy disk drive, CD-ROM drive, etc.

Disk crash

Physical failure of a diskette or hard drive that is generally not recoverable.

Disk density

Also known as area density, disk density is the measurement of the amount of data a disk can hold. The disk density is generally measured by the tracks per inch and/or bits per inch. A good example of disk density is high-density floppy diskettes that are capable of holding more information than a low density diskette.

Disk drive

Physical drive capable of holding information and/or retrieving information. A good example of a disk drive is the computer floppy disk drive.

Disk driver

Device driver that allows a specific disk drive to communicate with the remainder of the computer. A good example of this type of driver is a floppy disk driver

Disk duplexing

Method of how information is written to the hard disk drive. With disk duplexing, when information is needed to be written to a hard disk drive, instead of only one disk drive, it is copied to both drives, generally on different disk controllers.

Disk optimizer

Also known as disk compression, a disk optimizer is a software program designed to organize data and/or compress data allowing the disk drive to contain the maximum amount of information as possible.

Disk partition

Portion of a disk capable of holding data. This allows for a hard disk drive to be split into multiple segments allowing the computer to have multiple disk drives.

Disk partition table

Permanent structure which indicates to the operating system or boot record how information on a hard disk drive is to be laid out.

Disk platter

Magnetic metal or ceramic disk located inside the computer hard disk drive that holds the actual data.

Disk Thrashing

When referring to a computer, thrashing or disk thrashing is a term used to describe when the hard disk drive is being overworked by moving information between the system memory and virtual memory excessively. Thrashing is often caused when the system does not have enough memory, the system swap file is not properly configured, and/or too much is running on the computer and it has low system resources. When thrashing occurs, a user will notice the computer hard disk drive always working and a decrease in system performance. Thrashing is bad on a hard disk drive because of the amount of work the hard disk drive has to do and if is left unfixed will likely cause an early failure of the hard disk drive.

DriveTrust

A hard disk drive technology developed by Seagate that was first widely used with DVR’s and later introduced to personal computers with the Seagate Momentus 5400 FDE.2. This technology encrypts the data on the hard disk drive and only allows that data to be read by the device or computer the drive is installed in. Because this new innovation is built onto the hard disk drive computers can have these drives installed with no additional software or patches. In addition the drives have a feature that allow them to be instantly erased, which helps prevent any sensitive data being read when the drive is sold or used in another computer.

DS

Short for Drive Select, DS is a jumper setting found on disk drives that is similar to the more commonly used master jumper setting. When a disk drive such as a computer hard disk drive has its jumper set to DS this tells the computer that it’s the only drive connected to the cable or should be used as the primary drive (master drive) on the cable.

EB

Short for Exabyte, an EB is 1018 or 1,000,000,000,000,000,000 bytes.

EIDE

Short for Enhanced IDE, EIDE is the next generation of IDE interface that was developed by Western Digital and an interface commonly used on IBM compatible computers. EIDE supports data rates from 4 and 16.6 MBps. In addition to being faster than IDE drives, EIDE supports drives up to 8.4GB.Supports faster PIO modes 3 and 4 as well as multiword DMA modes 1 and 2. ATA-2 also adds additional support for LBA drives which allows support for drives larger than 528 MB. EIDE is also referred to as ATA-2, Fast ATA or Fast IDE.

External storage

Type of storage that is not part of the computer’s memory. Examples of external storage are floppy disk drives, hard disk drives, tape drives, etc.

FAT, FAT12, FAT32

Short for File Allocation Table, FAT is a method used by Microsoft operating systems to keep track of the contents of a disk; the table is a chart of numbers that correspond to cluster addresses on the hard drive. FAT12: The oldest type of File Allocation Table that uses 12-bit binary system. A hard disk drive formatted using FAT12 can use a maximum of approximately 16,736,256 volume size and today is no longer used. If your computer is running Windows 95 or above and your FAT within FDISK is being displayed as FAT12 it is likely that your hard disk drive is corrupted, bad or has a computer virus. FAT16: FAT utilizing a 16-bit binary system. Commonly found with Windows 3.x through Windows 95. FAT16, while becoming obsolete by FAT32, is still commonly found. FAT32: Enhanced File Allocation Table utilizing a 28-bit binary system, first used in Windows 95 OSR2 and more so in Windows 98, that saves disk space by using 4k Cluster. See FAT32 Page for extended information about FAT32.

FDISK

FDISK (pronounced eff-disk) is an external MS-DOS utility that is used to configure the fixed disk. The FDISK program allows you to delete, create, and partition different portions of the hard drive. FDISK is also used in Windows 95, Windows 98 and Windows ME; however, after the release of FAT32, there are different versions of FDISK available.

File size

The measure of space a file takes on a storage medium such as a computer hard disk drive. File sizes can be measured in bytes (B), kilobytes (KB), megabytes (MB), gigabytes (GB), terabytes (TB), and beyond.

Fixed disk

Term commonly used with Hard disk drives because most hard drives are commonly designed to not be easily removed from the computer.

Fixed storage

Medium not easily removed, for example, a hard disk drive. Fixed storage is often represented on a computer network as a drive capable of storing data.

Floating defects

Type of physical defect encountered on a hard disk drive where the disk drive heads become out of alignment causing random read/write errors.

FM

Short for Frequency Modulation, FM encoding is a method of recording data to a floppy disk and/or hard disk drive platter. This method of encoding is no longer used today and has been replaced with MFM.

FNR

Short for Format and Restore, FNR is a term often used by technicians to refer to proceeding with a format and restore of a computer system.

Format

The overall layout of a document. For example, the formatting of text on many English documents are aligned to the left of a page. Format is also a MS-DOS command that prepares a blank diskette or hard disk by first formatting the disk to hold data.

Fsck

Short for File System Check, fsck is a program run on Linux, Unix and their variants that checks the file system for any errors. For users who are familiar with Microsoft Windows, this command is similar to Microsoft’s scandisk command.

GB

Short for Gigabyte, GB is equal to 1,073,741,824 bytes, however the IEC defines a GB equal to 109 or 1,000,000,000 bytes. Therefore, a GB could be either of these values; many hard disk drive manufacturers and computer manufacturers will define what they consider a Gigabyte to equal in the fine print.

Hard disk

Rigid circular disk located inside a computer hard disk drive. The term hard disk is often used as an abbreviation to hard disk drive.

Hard drive

Computer’s main storage media device, also called a hard disk drive or abbreviated as HD or HDD. The hard drive was first introduced on September 13, 1956 and consists of one or more hard disks inside of air sealed casing. Most hard drives are permanently stored in an internal drive bay at the front of the computer and are connected with one ATA / SCSI cable and power cable. Below is an illustration of the inside of a hard disk drive.

Head

Device found on the arm of a hard disk drive that is used to read data from the hard disk drive’s disk platter.

Head positioning

Action performed by a computer hard disk drive that moves the hard disk drive head into its proper position and verifies nothing is malfunctioning with the head arm.

Head switching

Action taken by the hard disk drive head that moves the current action being performed on one read / write head to another.

IDC

Short for Insulation Displacement Contact or Insulation Displacement Connector, IDC is a type of connector found at the end of many cables. For example, an IDE disk drive or floppy disk drive cables have IDCs at the ends of the ribbon cable.

IDE

Short for Integrated Drive Electronics or IBM Disc Electronics, IDE is more commonly known as ATA and is a standard interface for IBM compatible hard drives. IDE is different from the Small Computer Systems Interface (SCSI) and Enhanced Small Device Interface (ESDI) because its controllers are on each drive, meaning the drive can connect directly to the motherboard or controller. IDE and its updated successor, Enhanced IDE (EIDE), are the most common drive interfaces found in IBM compatible computers today. Below is a picture of the actual IDE connector and cable.

Index mark

Also known as the index track, the index mark is a mark used to indicate the starting point of a track on a hard disk drive. This mark is commonly a small hole, gap or magnetic strip. The index mark allows a hard disk drive head to move quickly to various portions of the hard disk drive.

Interrecord gap

Also known as an Interblock gap and abbreviated as IBG or IRG, an Interrecord gap is a break between data records on hard drive and magnetic tape that serves as a safety margin for data overwrites. Interrecord gaps are also used as a marker for the end of data.

Interleave

When referring to a computer hard disk drive, interleaving is a method of making the read of data more efficient. Interleaving is a method of organizing the sectors on a computer hard disk drive, allowing data to be arranged so the read/write head can access information easier, making data read off the hard disk drive faster. Types of interleaving:

One-to-one = Sectors are placed on a track

Two-to-one = Sectors are spread out by other sectors.

Interrecord gap

Also known as an Interblock gap and abbreviated as IBG or IRG, an Interrecord gap is a break between data records on hard drive and magnetic tape that serves as a safety margin for data overwrites. Interrecord gaps are also used as a marker for the end of data.

USB flash drive

Also known as a USB flash drive, a jump drive is a portable memory disk, a jump drive is a small device (about the size of your index finger) that connects to a computer’s USB port and often is capable of storing 256MB, 512MB, or more. Jump drives are used by users who need an easy and small way to transfer or store information from their computer.

Kilobit

A kilobit, or Kb, is equal to 1,000 bits. When the b is uppercase (KB), this refers to a kilobyte.

Kilobyte

Abbreviated as K or KB, a Kilobyte is equal to 1,024 bytes; however, the IEC defines that one KB is equal to 1,000 bytes. Therefore, a KB could really equal either of these values. With a lowercase b (Kb), this refers to a kilobit.

LBA

Short for Large Block Addressing, LBA allows a PC computer to access hard disk drives larger than 528MB.

Low-level format

An initial formatting of a hard drive that initializes the physical tracks on the surface or the internal disks. The drive manufacturer usually performs a low-level format on the hard disk drive before it is released and is not something a user needs to do once they’ve purchased the drive. If a high-level format (i.e. running the MS-DOS format command) is unable to be completed on a hard disk drive and/or you’re looking for information about how to do a low-level format because of a MBR virus or being unable to delete partitions, a debug routine can be performed on the computer that is often referred to as a low-level format.

Lzone

Short for landing zone, lzone is setting used to specify the landing zone of the heads on a computer hard disk drive. Today, with new computers, the lzone is no longer required as most computer hard disk drives autopark.

Mass storage

Term used to describe a location with large quantities of data.

Master

A setting commonly adjusted using a jumper found on a computer peripheral, such as a hard disk drive or CD-ROM drive. This setting sets the drive to be the primary drive and allows for multiple devices to be connected to a single connection. Computers can only have one master per channel, this means there can only be one master drive on a single IDE/EIDE cable.

MBR

Short for Master Boot Record, MBR is also sometimes referred to as the master boot block and is the first sector of the computer hard disk drive used to determine from which partition a computer will boot. The MBR tells the computer where to find and how to load the operating system. It also tells the computer how the hard drive is organized and provides information about the drive’s partitions. The master boot record is located on the first sector of the hard drive; it’s the first program the computer runs after performing a memory check and looking for a bootable disk (if set in CMOS). The MBR is also susceptible to boot sector viruses that can corrupt or delete the MBR, which can leave the hard drive unusable and prevent the computer from booting up. A well-known MBR virus is the Monkey Virus.

Mb / MB

Mb is short for megabit and is 1,000,000 bits, or 106, Mb commonly usually expresses the rate at which data is transferred, for example, “10/100 Mbps” represents 10 or 100 megabits per second, the common speed of a standard network card. Also abbreviated as meg, MB is short for megabyte. A MB is a common measurement used with computer storage media. A Megabyte is equal to 1,048,576 bytes; however, the IEC defines that one MB is equal to 1,000,000 bytes, or 106. Therefore, a MB could really equal either of these values.

MBR

Short for Master Boot Record, MBR is also sometimes referred to as the master boot block and is the first sector of the computer hard disk drive used to determine from which partition a computer will boot. The MBR tells the computer where to find and how to load the operating system. It also tells the computer how the hard drive is organized and provides information about the drive’s partitions. The master boot record is located on the first sector of the hard drive; it’s the first program the computer runs after performing a memory check and looking for a bootable disk (if set in CMOS). The MBR is also susceptible to boot sector viruses that can corrupt or delete the MBR, which can leave the hard drive unusable and prevent the computer from booting up. A well-known MBR virus is the Monkey Virus.

Media

Term used to describe a type of computer storage. For example, a floppy diskette is a type of media used to store data.

MFM encoding

Short for Modified Frequency Modification encoding, MFM encoding is a method of how a disk controller records information onto a floppy disk and/or hard disk drive platter that replaced FM.

Partition

When referring to a computer hard disk drive, a partition is a segment of the hard drive that is separated from other portions of the hard disk drive. Partitions help enable users easily divide a computer hard disk drive into different drives and/or into different portions for multiple operating systems to run on the same drive. With older file allocation tables, such as FAT16, creating smaller partitions allows a computer hard disk drive to run more efficiently and save more disk space. However, with new file allocation tables, such as FAT32, this is no longer the case.

NTFS

Short for New Technology File System, NTFS is a file organizational system that stores and accesses information located on Microsoft Windows NT, Windows 2000, Windows XP operating system. NTFS offers better methods of data protection and file recovery than previous versions of FAT.

Park

When referring to a computer hard disk drive, park refers to a process of moving a computer hard disk drive head away from the disk platters to prevent the head from mistakenly damaging the disk platter when the computer or hard disk drive is being moved. In the past, older hard disk drives and operating systems required the user to manually park and unpark the hard disk drive using a software utility or program. Today, however, hard disk drives automatically park and unpark.

Permanent storage

Type of computer storage that keeps the data or its contents regardless if the power is turned off or if the storage device is moved to another computer. The most commonly used permanent storage is the computer hard disk drive.

PIO

PIO, or Programmed Input/Output, is a method of transferring data from a device to another device, utilizing the computer processor and not the memory or DMA. Because PIO modes utilize the computer processor, using PIO is slower than DMA.

PIO Mode Max Transfer Rate ATA Standard

Mode 0 3.3 MB ATA

Mode 1 5.2 MB ATA

Mode 2 8.3 MB ATA

Mode 3 11.1 MB ATA-2

Mode 4 16.6 MB ATA-2

Note: There are no plans, and likely will never be plans, for a PIO Mode 5 (or anything beyond Mode 4), although some computer and hardware manufacturers have advertised computer or hardware with acceptance to PIO Mode 5.

PK

Short for jumper park, PK is a disk drive setting that is similar to the more common slave setting found on most drives. When a drive is set to this setting it is configured as the secondary drive (slave drive).

Platter

An aluminium, glass, or ceramic disk that is coated in a magnetic media that is located within a hard disk drive and used to permanently store all your computer’s data. When the computer is turned on, these platters will begin to rotate at so many rotations per minute (RPM). This rate varies depending upon the model of hard drive you have; an example of how fast a hard drive may spin is 7200 RPM. As the disk platters are rotating, the read/write head accesses information on one of the platters. It is not uncommon for a computer hard disk drive to have multiple platters. To help store and retrieve the data from the platter, data is stored in tracks, sectors and cylinders on each platter.

Preformatted

Computer diskette, tape, hard disk drive, or other medium that has already been formatted and does not require the user to format the disk before using it.

RAID

Short for Redundant Array of Inexpensive Disks, RAID is an assortment of hard disk drives connected and setup in ways to help protect and/or speed up the performance of a computer’s disk storage. RAID is commonly used on servers and high performance computers

RAM disk

Also known as a RAM drive, a RAM disk is a software-generated disk drive that stores information in the computer memory instead of on a physical disk drive. Because information is stored and accessed directly from the computer memory, RAM disk drives are faster; however, they are much more expensive than a standard hard disk drive.

Redundant Array of Inexpensive Disks:

RAID is an assortment of hard disk drives connected and setup in ways to help protect and/or speed up the performance of a computer’s disk storage. RAID is commonly used on servers and high performance computers

Removable hard drive

A computer hard drive that has been placed within a plastic or metal cartridge that enables it to be removed easily and placed into other computers with similar removable bays.

Ribbon cable

A thin cable that resembles a car seat belt or duct tape. These cables are commonly the data cables used for devices such as a CD-ROM drive or a Hard disk drive. It is common for most ribbon cables found within a computer to contain a dotted stripe or line along one side of the cable, this line indicates which edge of the cable is pin one, helping the user connect the cable properly. In addition to one edge of the cable being marked, most ribbon cables used today are also keyed, making it possible to only connect the cable one way.

Rigid disk

The name of a disk or disc that is not flimsy like tape. A good example of rigid disks are the disk platters found in a hard disk drive; floppy diskettes, CDs, and Zip diskettes are also all considered rigid disks.

RLL encoding

Short for Run-Length Limited encoding, RLL encoding is a method of storing information on computer hard disk drives, floppy disk drives, CDs, DVD, and Blu-Ray that was originally invented by IBM. This method of storage is carried out by hardware in the disk controller and is less prevalent than the modified frequency modulation (MFM) encoding scheme.

RPM

Short for Revolutions Per Minute, RPM is used to help determine the access time on computer hard disk drives. RPM is a measurement of how many complete revolutions a computer’s hard disk drive makes in a single minute. The higher the RPM, the faster the data will be accessed; for example, if you were comparing two hard disk drives, one with 5400 RPM and another with 7200 RPM, the hard disk drive with a 7200 RPM will be capable of accessing data much faster than the 5400 RPM drive. However, it is also important to note that a 5400 RPM drive will be much cheaper than a 7200 RPM drive. While it may not be a noticeable speed difference when loading small files, the RPM of a hard disk drive can make a dramatic difference when loading large files and/or several hundred or thousand files. We always recommend users get at least a 7200 RPM drive.

SATA

Short for SerialATA, SATA 1.0 was first released in August 2001 and is a replacement for the Parallel ATA interface used in IBM compatible computers. SerialATA is capable of delivering 1.5Gbps (150MBps) of performance to each drive within a disk array, offers backwards compatibility for existing ATA and ATAPI devices, and offers a thin, small cable solution as seen in the below picture. This cable helps make a much easier cable routing and offers better airflow in the computer when compared to the earlier ribbon cables used with ATA drives.

SCSI

Short for Small Computer System Interface, SCSI, pronounced as “Scuzzy”, is a standard for parallel interfaces that transfers information at a rate of eight bits per second and faster, which is faster than the average parallel interface. SCSI-2 and above supports up to seven peripheral devices, such as a hard drive, CD-ROM, and scanner, that can attach to a single SCSI port on a system’s bus. SCSI ports were originally designed for Apple Macintosh and Unix computers, but also can be used with PCs. SCSI-1 is the original SCSI standard developed back in 1986 as ANSI X3.131-1986. SCSI-1 is capable of transferring up to eight bits a second. SCSI-2, approved in 1990, added new features such as Fast and Wide SCSI, and support for additional devices. SCSI-3 was approved in 1996 as ANSI X3.270-1996.

Sector

A division of a storage medium such as a hard drive or diskette. Diskettes or hard drive platters are divided into wedge shaped sections that segment the circular tracks into small arcs such as if you were to cut a pie into a section, each section is one arc. Each arc is a sector that typically holds 512 bytes of data. All of the arcs within a given wedge are given the same sector number for interleaving purposes, so the term sector may refer to the entire single arc. The size of sectors can be customized to maximize the storage area. For example, if a user stores smaller files, decreasing the sector size allows more files to fill the space without any leftover room.

Selector channel

A high-speed input / output (I/O) channel that links a peripheral device, such as a hard drive or CD-ROM, to the computer.

S.M.A.R.T.

Short for Self-Monitoring Analysis and Reporting Technology, S.M.A.R.T, or SMART, is a diagnostic method originally developed by IBM to test hard disk drives and was introduced with the ATA-3 specification.

Settling time

The time it takes a hard disk drive’s read / write head to move to a position. This time is commonly factored into the hard disk drive’s seek time.

Slave

Computer or peripheral device that operates under the control of another computer peripheral. A setting commonly adjusted using a jumper found on a computer peripheral, such as a hard disk drive. This setting sets the drive to be the secondary drive and allows for multiple devices to be connected to a single connection.

Soft-sectored disk

A disk that has had its sectors mapped with a software program instead of a physical separation created on the disk.

Source data disk

Term could also be source data disc, source data diskette, or source data drive, the source data disk is a diskette, disc, or drive from which data will be copied to an alternate diskette or disc. For example, when copying a floppy diskette to another floppy diskette the source data diskette is where the information is being copied from and the destination data diskette is where the information is being copied to.

Storage

Term used to describe a location where information can be held for later use. A computer commonly has two types of storage: internal and external. An internal storage is a device such as a hard disk drive, where an external storage may be a device such as a tape drive that utilizes removable diskettes to store information.

TB

A terabyte or TB, is equal to 1,099,511,627,776 bytes; however, the IEC defines a TB equal to 1012, or 1,000,000,000,000, bytes. Therefore, a TB could be equal to either of these values.

Thrashing

When referring to a computer, thrashing or disk thrashing is a term used to describe when the hard disk drive is being overworked by moving information between the system memory and virtual memory excessively. Thrashing is often caused when the system does not have enough memory, the system swap file is not properly configured, and/or too much is running on the computer and it has low system resources. When thrashing occurs, a user will notice the computer hard disk drive always working and a decrease in system performance. Thrashing is bad on a hard disk drive because of the amount of work the hard disk drive has to do and if is left unfixed will likely cause an early failure of the hard disk drive.

Track

When referring to an audio CD, a track is a section of a CD that contains a single, full song. Tracks are used on a CD to help enable a user to skip songs or locate a song on a CD easily. A track is also a data storage ring on a computer floppy diskette or hard disk drive that is capable of containing information. As shown in the below example, a track goes all around the platter and is used to help locate and retrieve information from a disk or diskette.

UDMA 

Short for Ultra-DMA and also known as Ultra ATA, UDMA is a standard developed by Quantum in conjunction with Intel that is twice as fast as the previous DMA interface. UDMA was first introduced in 1998 with the ATA-4 or ATA/ATAPI-4 standard and is capable of transferring data at 33.3 MBps, which is how the UDMA/33 or Ultra-DMA/33 names came about. Since its initial release and the approval of new ATA standards, the below UDMA standards are available.

ATA-5 — UDMA/66, Ultra-DMA/66

ATA-6 — UDMA/100, Ultra-DMA/100

Notice: UDMA/66 and higher are only supported when an 80-wire 40-pin cable is being used. This cable can be distinguished by looking at the ribbon and noticing the amount of wires when compared with a 40-wire cable.

Voice coil

When referring to a computer hard drive, a voice coil is a type of motor used to move the access arm within a hard disk drive.

Volume label

With IBM compatible computers a volume label is a unique name commonly assigned by the user to a storage medium. For example, a user is capable of changing the label on a floppy disk to describe what may be on a diskette.

Winchester disk

Named after the .30-caliber Winchester rifle, Winchester disk drive is a hard disk drive developed by IBM that had two 30MB capacity and offered a 30 millisecond (ms) access time.

Wpcomp

Short for Write Pre-Comp, wpcomp is a setting used with computer hard disk drives that specifies when adjustments are to be made when writing inside tracks of a hard disk drive platter.

Zoned recording

Method hard disk drive manufacturers use to increase the available hard disk drive space by increasing the amount of sectors per track. This enables outer tracks to have more sectors than inner tracks. In the past, a hard disk drive had the same amount of sectors on each of its tracks.