Page III: In this issue of Industry Insider, Linus Wong, our guest columnist from Adaptec Storage Solutions, traces the origins of Serial ATA (SATA), a relatively new connectivity interface.
Some Serial ATA proponents predict that SATA II Extensions will ultimately replace the SCSI protocol, a highly unlikely outcome since SCSI's robustness for enterprise applications comes from 20 years of industry investment. That work has produced interfaces that deliver the highest levels of system reliability, scalability, performance and manageability. All the major enterprise interface technologies - including iSCSI, Fibre Channel, parallel SCSI and Serial Attached SCSI - use the proven SCSI protocol.
Another barrier to Serial ATA's use in I/O-intensive transactional environments is total cost of ownership. While Serial ATA disk drives carry a much lower purchase price than enterprise-class drives, the ongoing hardware and management costs from frequently replacing failed drives not designed to withstand transactional workloads overshadows any initial cost advantage. Serial ATA disk drives, for example, lack the mechanical heft and sophistication to support fast seek times, the random data patterns typical of transactional workloads, and the tolerance to rotational vibration caused when multiple drives in a single enclosure are seeking simultaneously.
SCSI is undergoing the same transition as ATA, moving from a parallel to a serial architecture, namely Serial Attached SCSI. In doing so, Serial Attached SCSI will generate a larger potential base of customers for Serial ATA storage since the Serial Attached SCSI interface will support both Serial Attached SCSI and Serial ATA disk drives. Serial Attached SCSI will maintain backward compatibility with existing Serial ATA connectors and cables, allowing IT managers to populate a single dual-mode controller or backplane with either drive type depending on the workload or application.
Serial Attached SCSI is the follow-on technology to Ultra320 SCSI and will ultimately be the primary disk interface used in enterprise-class servers. Serial Attached SCSI also offers a performance roadmap extending from 3 gigabits per second to 12 gigabits per second, the unique ability to aggregate ports for scalable bandwidth and external cabling for connecting JBODs (just a bunch of drives).
The Serial Attached SCSI 1.0 specification was completed and ratified by INCITS (InterNational Committee for Information Technology Standards) in December 2003. At the same time, the Serial ATA II Extensions 1.1 specification is nearing completion pending final changes and clarifications. The first Serial Attached SCSI plugfest to demonstrate broad Serial Attached SCSI interoperability among early products was held in March. Serial Attached SCSI products will be available by the end of 2004.
After launching in 2003, Serial ATA controllers are now shipping in volume, an increase driven largely by greater disk drive availability.
Serial Attached SCSI is changing the way IT managers and systems builders are thinking about deploying disk drives in enterprise environments. For the first time, a single backplane will support the deployment of both enterprise and desktop disk drives. As a replacement for SCSI, Serial Attached SCSI disk drives will serve workloads where reliability and transaction processing are chief concerns. Optimised for cost-per-gigabyte, Serial ATA disk drives address the growing need for low-cost reference information storage. By supporting both disk drive types, Serial Attached SCSI backplanes will be the primary interconnect infrastructure for both reference and transactional data in enterprise environments.
As a result, Serial ATA disk drives will find still a wider market once Serial Attached SCSI systems are available. In time, most Serial ATA disk drives in the enterprise will be connected to a Serial Attached SCSI infrastructure for two reasons: the Serial Attached SCSI interface offers unprecedented storage configuration flexibility and simplifies component design, testing, qualification, and inventory control while reducing related costs for system builders and IT managers.
biography
Linus Wong is strategic marketing group director at Adaptec Storage Solutions.
If you would like to become a ZDNet Australia guest columnist, write in to Fran Foo, Editor of Insight, at fran.foo@zdnet.com.au.
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I think a lot of the problem with the uptake is that it (currently) provides little benefit. It is no secret that many of the SATA drives simply have a PATA->SATA convertor on the drive itself. At the motherboard side, it is a similar story.
Many of the drives were designed with the restrictions that come with PATA. Changing the interface and cable may give the device more potential to be quicker, but many existing devices are throttled so they can work on either.
In short, we have the option of paying more money for no noticable improvement in speed. The seek time and MB throughput (the figures that actually make the thing faster or slower) are identical.
Can't imagine why it hasn't taken the world by storm ...