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New arrays with a mix of SAS and SATA drives let you set up tiering in a single box. But proceed with caution: Numerous inoperability issues
need to be resolved.
The emerging class of mixed SAS and SATA storage systems could be the next big disruptive technology. Mixing high- and low-cost SAS and SATA disk drives within the same system, at interconnect speeds comparable to Fibre Channel (FC), is a recipe for significant change and opens the door to data lifecycle management (DLM).
Most major storage vendors will release mixed SAS and SATA disk drive storage systems by early to mid-2008. The price of these systems is expected to drop below that of mixed FC/SATA arrays, and storage vendors will be jockeying for position. A spokesperson for Network Appliance (NetApp) Inc. says combining SAS and SATA drives in the same system is critical to the company's future product lines.
However, issues unique to SAS/SATA mixed-drive products are starting to emerge. For example, Overland Storage Inc. recommends users separate SAS and SATA disk drives in its new Ultamus RAID 1200 because the vibrations caused by the higher speed 15,000 rpm SAS disk drives cause slower spinning 7,200 rpm SATA disk drives with lower vibration tolerances to fail. Winchester Systems Inc. had to withdraw its FlashDisk HyperSAN SF-2300 Series SAS and SATA storage systems from the market partly due to the negative experiences that resulted from mixing SAS and SATA disk drives.
To address these issues, vendors are writing firmware code and testing specific disk-drive layouts in shelf drawers to minimize interoperability problems. Some vendors are introducing clustered and modular storage system designs that better exploit the inherent benefits mixed SAS and SATA storage systems can deliver. The degree to which users can capitalize on this mix of SAS and SATA drives varies in direct proportion to the management software vendors provide to migrate data between the different tiers of disk.
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