SAS and SATA compatibility: a new paradigm for disk interconnects - Tape/Disk/Optical Storage

Computer Technology Review, June, 2003 by Mike Wall

ATA disks are widely used in desktop and mobile PCs where cost is a dominant consideration. ATA drives have lower MTBF than SCSI drives and are generally tested in less-stringent environments over shorter periods of time. The common ATA drive rotational speed is approximately 7200 RPM, with the norm typically one to two generations behind the rotational speed of common SCSI drives. Slower speeds enable higher capacity so ATA drives tend to have a higher capacity than SCSI drives. These features enable ATA drives to be priced significantly lower than SCSI drives with comparable capacity. There are situations where cost and capacity are higher concerns than performance and SCSI features. In these scenarios, SATA will be the preferred interface choice.

SAS will change the landscape of disk interconnects, because its inherent compatibility with SATA drives will enable unprecedented levels of flexibility with lower overall system costs.

www.intel.org

www.scsita.org

Table 1

Benefits of serial interface technologies

Serial Technology Features       System Benefits

Point-to-point topology          Dedicated disk connections
                                 with scalable throughput

Performance starts at 1.5Gb/s    Future performance and
(150 MB/s) for Serial ATA and    investment protection
3.0Gb/s (300MB/s) for Serial
Attached SCSI.

Fewer signals than parallel      Easier routing for higher
buses                            density

Thinner cables                   Improved chassis airflow

Disk/backplane interoperability  Flexible Serial Attached SCSI
                                 and Serial ATA deployment
                                 options

Mike Wall is a co-general manager, Storage Components Division, at Intel Corporation (Chandler, Ariz.). He is also a member of the SCSI Trade Association (San Francisco, Calif.)