Serial ATA (SATA) disk drives have only been shipping for about a year, but already the industry is cranking up the next version, SATA II, which doubles the data transfer rate to 3Gb/sec. The new standard is intended to match the speed of serial-attached SCSI (SAS) disk drives, due out in 2005.
"This will ensure that there will not be a bottleneck when SAS comes out at 3Gb/sec," says Barbara Murphy, vice president of marketing for storage products at AMCC Storage, formerly 3Ware. At 1.5Gb/sec, the original SATA drives could create a bottleneck when data is moved from 3Gb/sec SAS drives, as part of a data tiering strategy.
The faster SATA II drives also allow the use of port multipliers to link multiple drives to a single host, explains Justin Heindel, product marketing manager at Marvell, a semiconductor manufacturer. In general, "as the internal transfer rates of the drives increase, you need this headroom," he says.
The objective is to keep the interface I/O rate ahead of the disk's data rate. "If we did nothing, in two years the data rate off the disk would be faster than the interface rate," says Marc Noblitt, manager of interface planning at Seagate. To avoid this, vendors need to test the next jump in performance and begin introducing products one to two years in advance of when customers will need them.
The storage industry took the first step in that direction in September when Seagate, Marvell and AMCC demonstrated working components that proved the performance of the 3Gb/sec specification. "This was a technology demonstration, not a product announcement. All we did was prove the speed, prove that the specification works," says Noblitt. In the coming months, vendors will begin rolling out controllers followed by disk drives that conform to the 3Gb/sec specification.
Don't expect SATA II to take over all at once--mixed-speed environments will be the norm for some time, thanks to SATA II's speed negotiation capability, explains Murphy. And no sooner will 3Gb/sec drives ship that vendors will turn their attention to the next standard--probably 6Gb/sec.
Some products may begin shipping soon. "There already are products on the host side today that support 3Gb/sec," says Noblitt. Most storage vendors will have products available before 2006. The first products may carry a slight price premium initially, but prices will drop quickly as production ramps up.