Report: SATA & SAS to Share Systems

Serial Advanced Technology Attachment (SATA) and Serial-Attached SCSI (SAS) disk drives will coexist in a single box as early as next year, according to a report from Byte and Switch Insider, this publication's paid subscription research service. But don't expect them to displace Fibre Channel drives anytime soon.

The report, "SATA and SAS: Serious About Serial," looks at the impact the serial-attached interfaces will have on external storage. SATA already serves as a mid-range complement to expensive Fibre Channel disk and low-cost tape drives, and SAS drives should start showing up in many of the same devices over the next year, the report says.

Why? Using SATA and SAS in the same system fits an increasingly popular strategy of transferring data to different media as it ages. Companies can move data from SAS to cheaper SATA disks as they need to access it less frequently. The expectation is that Fibre Channel will be used for primary (or online) storage, with SATA and SAS used for nearline or archived storage.

It makes sense for drive vendors to include both SATA and SAS in one box. SAS connectors are form-factor compatible with SATA, and SATA connector signals are a subset of SAS signals, so that SATA drives can plug directly into SAS environments.

On the other hand, SAS drives do not work on a SATA controller, so devices that mix SAS and SATA will do so via a universal SAS backplane providing connectivity to both. Watch for vendors to take advantage of the compatibility with early SAS products. For instance, Ario Data Networks announced that its first SAS controller, due later this year, will attach to SATA II devices. Clearly, customers will need to think about whether to jump onto SATA-only gear today, or opt to wait for SAS equipment that may have more potential value for them in the long run.Bottom line? For the foreseeable future, SATA will be used primarily as economy-class hardware for secondary storage. When SAS becomes available, it will sit between high-end Fibre Channel and low-end SATA, as parallel SCSI does today.

The report looks at the SATA strategy of major subsystem vendors, including:

Dave Raffo, Senior Editor, Byte and Switch

More information about the current Byte and Switch Insider report, "SATA and SAS: Serious About Serial," is available here