Looking ahead to serial SCSI
New interfaces may alter the disk drive market’s courseFollow @infoworld
Over the years, disk drives have gone through numerous changes in their size, reliability, recording technology, and connectivity interface. SATA (Serial ATA) adds yet another interface to the existing list of parallel ATA, SCSI, and FC (Fibre Channel) drives. This means we’ll soon be hearing a familiar refrain: Another major change to the way we connect disk drives to their host is right around the corner.
Expected to begin shipping in 2004, SAS (Serial Attached SCSI) will offer interesting features, such as smaller cables and connectors, and full duplex connections, addressing thousands of devices per port and an initial transfer rate of 3Gbps.
Furthermore, the smaller connectors will allow for dual-ported SAS drives, reducing the risk of a failing controller and extending the compact 2.5-inch format to enterprise-class drives, with obvious benefits in space and power requirements. As does SATA, SAS will have point-to-point connections; but by using expanders — essentially, fan-out devices — the new protocol makes it possible to address multiple devices from a single port.
Add to this the ability to connect both SAS and SATA devices to the same controller (but on different ports) and the possibility of combining the speed of multiple ports into a single connection, and it’s easy to understand that the new protocol will consolidate the best characteristics of SCSI, FC, and SATA into a single interface.
How will SAS affect the drive market? An easy prediction is that devices with parallel interfaces will gradually disappear and be replaced by SAS devices for transactional, mission-critical applications and SATA for everything else. FC devices should maintain their high-end niche, but SAS solutions could extend their reach even further and do some nibbling on that space as well.
With that in mind, will other vendors follow Western Digital’s example, offering high-performance drives with SATA interface? I doubt it. Combining SAS and SATA solutions may promise technical and monetary benefits that are unattainable today, but expect to see the best drive performance and reliability specs labeled SAS.