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.
-- 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.
SAS generational upgrades can be easily implemented because of the retention of the parallel SCSI
data protocols when it was developed.
Backup administrators needed to use a Fibre Channel to parallel SCSI
protocol converter (also called a Bridge or Router) to connect their native SCSI drives and libraries to the Fibre Channel SAN.
As predicted, the market is making an orderly transition from Parallel SCSI
to SAS as the mainstream server storage interface of choice.
The GigaStorATX integrated into the ASUS i316-A1 iSCSI SAN array directly replaces parallel SCSI
in DAS and NAS environments and supplement/replace FC in SAN environments.
Enterprise servers have long used the standard parallel SCSI
SAS is the next generation SCSI interface that delivers significant improvements in scalability, performance, reliability, and flexibility over parallel SCSI
by leveraging a serial architecture for data transport.
Many current systems employ Ultra 320 parallel SCSI
for boot drives, local data storage, or external arrays of modest size.
The iStor inAbled aXstor Ai iSCSI-SATA Storage Subsystem replaces parallel SCSI
in DAS and NAS environments and supplements or replaces FC in SAN environments.
As the follow-on to the widely deployed parallel SCSI
interface, SAS brings a number of benefits to the broadcasting and video industry.
Data centers have relied on the parallel SCSI
bus interface as the workhorse of disk drive interconnections for almost 25 years.