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A
| Acoustic Noise | The level of sound the drive produces while operating, the smaller the number,the better |
| Access | The level of sound the drive produces while operating, the smaller the number,the better |
| Access time | Access time measures the time lapsed between the access command and the point in time where the head is positioned to read or write a specific sector (address), measured in milliseconds (ms). (The access time for HDDs is a combination of seek time, controller overhead, and rotational latency, i.e. time taken for desired sector to rotate under head for access) |
| Actuator | The mechanism that moves the head(s) to the correct cylinder. It generally comprises of two parts; a rotary voice coil and head gimble assembly. The actuator arm houses the head at the tip of its arm |
| Address | The precise location of specified data on a disk. The address primarily consists of three components (Cylinder Address, Head Address, Sector Address) |
| Allocation | Assigning certain areas of a disk to particular data |
| Allocation Unit (also sector or cluster) |
A number of sectors on a disk that are reserved for storing particular data |
| Areal Density | Bit density; Bits per Inch (BPI) x Tracks per Inch (TPI). This reflects how dense the data is stored on the media of the HDD |
| ATA | Advanced Technology Attachment (also EIDE), a standardised (IBM compatible) interface. ATA has been upgraded overtime |
| ATA-2 | Enhanced IDE (E-IDE),faster PIO/DMA mode, LBS Addressing, Improved 'Identity Drive' Command (Plug'n'Play) |
| ATA-3 | Fast ATA (E-IDE), PIO Mode 4, S.M.A.R.T., Simple password, more sophisticated power management |
| Atapi | ATA packet interface, a communications protocol which allows the electronic controllers for IDE hard disk drives to handle up to four devices, including CD-ROMs and tape drives and tape drive, Atapi devices plug into the IDE Interface |
| ATA-4 | Merge of ATA-3 and Atapi into one, Strong command overlap |
| Ultra-ATA | A high performance Ultra DMA (transfer rate of 33 MB/s) |
| Ultra-ATA | A new, even higher performance Ultra DMA (transfer rate of 66 MB/s) |
| AV | Audio Visual. AV drives denotes drivers modified to enhance transfer rate performance for specific applications |
| Average Latency | The average amount of time it takes for the drive to rotate to the correct address, so that the head can begin reading or writing in its desired location (is derived from the spindle speed) |
| AVI | Audio video interleaved. A standard system, form Microsoft, for integrating sound and vision for Windows into a single file for hard disk or CD-ROM |
| Average Seek Time |
The average time for a head to seek the address, calculated over a large number of random seeks |
