23 Aralık 2007 Pazar


Serial Advanced Technology Attachment is a computer bus primarily designed for transfer of data between a computer and storage devices (like hard disk drives or optical drives).

The main benefits are faster transfers, ability to remove or add devices while operating (hot swapping), thinner cables that let air cooling work more efficiently, and more reliable operation with tighter data integrity checks than the older Parallel ATA interface.

It was designed as a successor to the legacy Advanced Technology Attachment standard (ATA), and is expected to eventually replace the older technology (retroactively renamed Parallel ATA or PATA). Serial ATA adapters and devices communicate over a high-speed serial cable.

Standardized in mid-2004, eSATA defined separate cables, connectors, and revised electrical requirements for external applications:

* Minimum transmit potential increased: Range is 500–600 mV instead of 400–600 mV.
* Minimum receive potential decreased: Range is 240–600 mV instead of 325–600 mV.
* Identical protocol and logical signaling (link/transport-layer and above), allowing native SATA devices to be deployed in external enclosures with minimal modification
* Maximum cable length of 2 m (USB and FireWire allow longer distances.)

eSATA enters an external storage market already served by the USB and FireWire interfaces. Most external hard disk drive cases with FireWire or USB interfaces use either PATA or SATA drives and "bridges" to translate between the drives' interfaces and the enclosures' external ports, and this bridging incurs some inefficiency. Some single disks can transfer almost 120 MB/s during real use, more than twice the maximum transfer rate of USB 2.0 or FireWire 400 (IEEE 1394a) and well in excess of the maximum transfer rate of FireWire 800, though the S3200 FireWire 1394b spec reaches ~400 MB/s. Finally, some low-level drive features, such as S.M.A.R.T., are not usable through USB or FireWire bridging. eSATA does not suffer from these issues.

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