access time
The period of time the elapses between a inquiry for details from disk or memory and also when the information arrives in ~ the requesting device. Memory access time refers to the time that takes to deliver a personality from memory to or indigenous the processor, and disk access time refers to the time that takes to place the read/write heads end the requested data.

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active terminationA method for end a daisy chain the SCSI tools in which the terminator consists of (in enhancement to terminating resistors) voltage regulators that proactively take terminator strength from the SCSI bus itself and also use it because that powering the termination of the bus.
actuator armThe maker inside a hard disk drive that moves the read/write heads as a team in the fixed disk.
AT attachment 3 (ATA-3) InterfaceA minor review of the ATA-2 user interface specification that introduced several renovations over ATA-2, including SMART.
AT Attachment interface (ATA)The initial specification for how two ide hard disks connect together and also communicate through the hold computer. Also known as ATA-1.
AT Attachment user interface with Packet user interface (ATAPI) ExtensionAn expansion to the ATA interface specification that permits devices besides tough drives (like CD-ROM drives) to interact with the computer using the exact same cabling as ATA tough drives.
AT Attachment v Packet interface (ATA/ATAPI-6)Version 6 of the ATA traditional (with ATAPI support) that has support because that the attributes of all earlier versions that the ATA standard and also includes support for brand-new features such as 100MBps (TJItraDMA/100) and also a48-hit LBA address length.
AT Attachment with Packet lnterface-5 (ATA/ATAPI-5)Version 5 of the ATA standard(with ATAPI support) that includes support for all attributes of the ATA requirements before(versions 1 v 4) as well as brand-new Ultra DMA modes, causing obligation 80 conductor cable, and the remove of outdated ATA commands.
ATA version 2 (ATA-2)The second version the the original ide (ATA) specification that enabled drive size of several gigabytes and overcame the limitation of 528MB. It is additionally sometimes generically well-known as intensified IDE (EIDE).
ATA/ATAPI-4Fourth review of the ATA standard. Includes ATA features, plus support for ATAPI and a new cable architecture (80-wire, as opposed come the 40-wire cable used on previously revisions of the standard).
ATA/ATAPI-7The newest, suggest ATA/ATAPI conventional (proposed together of feather 2003). To incorporate such features as serial ATA and a 150MBps deliver rate.
ATA-2The second revision that the ATA standard. Includes support because that logical block addressing(LBA), which permits for drives bigger than 528MB, assistance for PIO modes 3 and also 4, and also multi-word DMA modes 1 and 2.
ClusterThe smallest unit of tough disk room that DOS deserve to allocate come a file, consists of one or an ext contiguous sectors. The variety of sectors consisted of in a cluster depends on the tough disk type.
CMOS setup programA routine that modifies the computer?s setups in the CMOS memory the stores the configuration information for the computer. The is accessed by a special an essential or key combination at startup.
Cyclical Redundancy inspect (CRC)An error-checking regime that operation a mathematics formula versus the data gift transmitted. A an outcome is computed and also sent with the data. When the data come at the destination, the very same formula is run against the data-. If the results are the same, the transmission is taken into consideration successful.
CylinderThe cumulative name for every the tracks at the exact same concentric place on a disk. A difficult disk is composed of 2 or more platters, each with two sides. Each side is further divided into concentric circles recognized as tracks.
cylinder, Head, ar (CHS) addressingA technique of accessing each block the data by its cylinder, head, and also sector address. To compare to LBA address size expansion.
daisy-chainingA sample of cabling within the cables run from the an initial device come the second, 2nd to the third, and also so on. If the gadgets have both an ?in? and also an ?out,? the in the the very first device of every pair is linked to the out of the second device of every pair.
data compressionAny technique of encoding data so the it rectal less an are than in its initial form.
disk sectorThe part of a hard disk monitor that drops in a details section of the ?pie slice? ~ above the disk.
drive geometryTerm provided to define the number of cylinders, read/write heads, and also sectors in a hard disk.
drive holeThe feet in a floppy decaying that permits the engine in the disk drive to spin the disk. Also known together the hub hole.
EncodingA procedure by which binary details is changed into flux transition patterns top top a decaying surface.
FATSee document allocation table (FAT).
file assignment table (FAT)A table preserved by DOS or OS/2 the lists every the clusters easily accessible on a disk. The FAT includes the location of each cluster, and also whether it is in use, easily accessible for use, or damaged in sonic method and thus unavailable. The FAT additionally keeps monitor of which piece belong come which file.
fixed diskA decaying drive that contain several disks (also recognized as platters) stacked with each other and mounted through your centers on a small rod. The disks rotate as read/write heads floating above the disks make, modify, or sense changes in the magnetic location of the coatings on the disk.
flux transitionThe visibility or absence of a magnetic ar in a fragment of the coating ~ above the disk. As the disk passes over an area, the electromagnet is energized to reason the material to it is in magnetized in a small area.
hard decaying driveA storage maker that provides a collection of rotating, magnetically coated disks referred to as platters to store data or programs. A common hard disk platter rotates at as much as 7200rpm, and the read/write heads float on a cushion of waiting from 10 come 25 millionths of an inch thick so that the heads never come into contact with the recording surface. The totality unit is hermetically sealed to prevent airborne contaminants native entering and interfering v these close tolerances. Hard disks selection in capacity from a couple of tens of megabytes to numerous gigabytes of warehouse space; the larger the disk, the an ext important a well-thought-out backup strategy becomes.
High Voltage Differential (HVD)Support for differential signaling added to SCSI-2.
high-level formatThe process of prepare a floppy disk or a tough disk partition for usage by the operation system. In the situation of DOS, a high-level style creates the hoot sector, the file allocation table (FAT), and also the source directory.
IDE (Integrated journey Electronics)A tough disk an innovation that can affix multiple cd driver together. These drives combine the controller and drive right into one assembly. This provides them an extremely inexpensive. As a result, principle drives space the most commonly used disk technology installed in computer systems today.
Integrated journey ElectronicsSee principle (Integrated drive Electronics).
InterleavingA process that requires skipping sectors to write the data, instead of composing sequentially come every sector. This evens the end the data circulation and permits the drive to keep pace through the rest of the system. Interleaving is provided in ratios~. If the interleave is 2:1, the disk skips 2 minus 1, or 1 sector, between each sector it writes (it writes come one sector, skips one sector, and then writes to the following sector following). Most drives currently use a 1:1 interleave, since today?s drives are really efficient at transporting information.
LatencyThe time that elapses in between issuing a request for data and starting the data transfer. In a hard disk, this translates right into the time that takes to place the disk?s read/write head and also rotate the disc so the the forced sector or cluster is under the head. Latency is simply one of many factors that affect disk-access speeds.
LevelsIn RAID, the various approaches used for writing to disks come ensure redundancy. Every level is designed for a details purpose.
Logical Block Addressing (LBA)A technique of overcoming the 528MB maximum journey size design limitation the the combination of ATA and the BIOS?s the the time. Rather than accessing each block of data by its cylinder, head, and also sector attend to (known as Cylinder, Head, Sector(CHS) addressing), LBA states that every block ~ above the disc be offered its own distinctive ID number, which is 28 bits lengthy (a preferably of 137GB precious of addresses).
Low Voltage Differential (LVD)A feature set introduced with SCSI-3 that boosts the best SCSI bus length to 25 meters (82 feet) and increases the maximum feasible throughput to 80MBps (on Ultra3 broad LVD).
low-level formatThe procedure that creates the tracks and sectors ~ above a empty hard decaying or floppy disk; sometimes dubbed the physics format. Most hard disks are already low-level formatted; however, floppy disks get both a low- and a high-level layout (or logical format)when you use the DOS or OS/2 command FORMAT.
master driveThe primary drive in an concept master/slave configuration.
multiword DMA modeA data transfer setting that transfers numerous words at a time in a kind of burst. Multiword transfer is used much more with later on ATA specifications because of the incompetent of setting up a link to carry a solitary word every time. That sets increase the connection, transfers multiple indigenous of data, and then closes the connection.
optical driveA type of storage drive that offers a laser to read from and also write come the storage medium.
PacketA team of hits all set for infection over a network. It has a header, data, and a trailer.
passive terminationA method of SCSI bus discontinuation wherein you have to install terminating resistor package on the end of the buses.
PIO modesA an approach of data transport in i m sorry the computer?s CPU and also supporting hardware directly regulate the transfer of data between the hard disk and the rest of the computer. Most often, DMA is used in favor of PIO modes (especially ~ above PCI-based systems).
PlattersSeveral disks within the hard drive that room stacked with each other and mounted through their centers top top a tiny rod dubbed a spindle. As the platters rotate, one or more read/write heads float above the decaying surfaces and also make, modify, or sense changes in the magnetic location of the coatings ~ above the disks.
Programmed I/O (PIO)See PIO modes.
read/write headThat part of a floppy-or hard-disk device that reads and writes data to and also from a magnetic disk.
removable mediaAny warehouse media that have the right to be eliminated from the system.
SCSI adapterA device used to regulate all the devices on the SCSI bus and to send and retrieve data from the devices.
SCSI addressA unique resolve given to every SCSI device.
SCSI busAnother name for the SCSI interface and also communications protocol.
SCSI chainAll the devices connected to a single SCSI adapter.
SCSI terminatorA terminator on the SCSI interface. The SCSI interface must be appropriately terminated to prevent signals echoing on the bus. Countless SCSI devices have built-in terminators that interact when they room needed. With sonic older SCSI devices, you have to include an exterior SCSI terminator the plugs right into the device?s SCSI connector.
seek timeThe time the takes the actuator eight to move from rest position to energetic position because that the read/write head to accessibility information. Often used together a power gauge that an individual drive. The major part that a hard disk?s access time is actually look for time.
Serial ATAAn implementation the the ATA interface that functions over lot smaller cables and operates serially (as opposed to the present implementation the operates via parallel signal lines). The is feasible to to buy Serial ATA controllers and drives, but they room not necessarily an implementation of ATA/ATAPI-7.
single-word DMA modeA data deliver mode through which data is transferred one word in ~ a time, in contrast to multiword DMA transfer.
slave driveThe an additional drive in an concept master/slave disc configuration.
spin speedAn point out of how rapid the platters on a solved disk room spinning. Spindle The rod top top which platters are mounted in a tough disk drive.
terminating resistor packA tiny package that resistors used for terminating SCSI drives. See likewise terminator.
TerminatorA machine attached to the last peripheral in a series or the critical node ~ above a network. A resistor is placed at both ends of a coax Ethernet cable to avoid signals native reflecting and also interfering with the transmission.
TrackThe concentric circle unit of hard disk division. A disk plate is divided into this concentric circles.
UItraDMA IDEAlso recognized as ATA variation 4 (ATA-4). A technology that have the right to transfer data at33Mbps or faster, so it is likewise commonly seen in motherboard specifications as UItraDMA/33, Ultra66, Ultra100, or UDMA.
VolumeA called chunk of disc space. This chunk have the right to exist on part of a disk, can exist on all of a disk, or can expectations multiple disks. Volumes provide a way of organizing disk storage.
WordIn binary communications, multiple bytes linked together.

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write-protect tabThe tiny notch or tab in a floppy disk the is offered to write-protect it.