Accordingly, SAS will advance to dominate the direct-attach server space, parallel SCSIs
While parallel SCSI
limited users to 15 drives per controller, SAS architecture supports up to 16,384 connections for much greater scalability.
The Ultra160 uses a SPI-3 third generation parallel SCSI
interface, which adds five new features: (1) Fast-80 or a data bus speed running at 80 MHz; (2) Cyclic Redundancy Check (CRC)--a common error checking protocol, which is used to ensure data integrity as a safety measure since transfer speeds were being increased, leading to the possibility of data corruption; (3) Domain Validation, which improves the robustness of the process by which different SCSI devices determine an optimal data transfer rate; (4) Quick arbitration and selection (QAS), which represents a change in the way devices determine which device has control of the SCSI bus.
The Parallel SCSI
Adapter includes peripheral support for CD-ROM, fixed disk, Bernoulli, Syquest, scanners, optical jukebox, multifunction optical, WORM, Floptical disk, and tape drives.
- Parallel SCSI
-- This low cost interconnect supports a maximum of 15 devices and is limited by the electrical performance of parallel interconnects.
Traditional parallel SCSI
bus connections have been limited to a total of 7 or 15 storage devices.
On average, a native Fibre Channel tape drive costs around $500 more than the same drive with a parallel SCSI
Requirements like these for large volume data storage, compounded by fast query requirements are stretching the processing capability of parallel SCSI
SAS and SATA, with their increased connectivity permit use of volumes that are larger than with parallel SCSI
, and potentially have higher random throughput performance.
Serial Attached SCSI, the successor to the parallel SCSI
interface, leverages SCSI functionality and features while expanding SCSI's proven performance, scalability and reliability for enterprise storage.
ran its course from Wide Ultra to Ultra 2 and so on until Ultra 320, the latest version which transmits data at 320 megabytes per second.
As noted earlier, they require either costly bridges or deployment of their own infrastructure, separate from an enterprise's current Fibre Channel or parallel SCSI