HP Doubles Up on 2.5-Inch SAS Drive Capacity - Page 2

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Because 10k drives are used for less time sensitive activities like archiving, where instant response is not as vital, he said a 3.5-inch Serial ATA drive, the kind used in regular desktop computers, is often good enough. Those drives spin at 7,200 RPM but are at the 1 terabyte level, so one 1TB SATA drive can often be good enough for performance needs, and certainly cheaper than three 300GB SAS drives.

HP maintains that it can get greater performance with 2.5-inch 10k drives over 3.5-inch 15k drives thanks to numbers. A 2U drive bay can hold 25 2.5-inch drives, whereas a 3U bay can only hold 14 3.5-inch drives. More spindles means more IOPS, said Daley. A 2U bay of 2.5-inch drives has 40 percent higher IOPS than the 3U bay of 3.5-inch 15k drives simply because there are more drives to spin at once, while still consuming 12 percent less power.

Future developments

Daley said HP and Seagate are working on 2.5-inch 15k drives, which currently max out at 72GB capacity. The largest 3.5-inch 15k drive has 450GB of capacity. Because they spin so fast – 250 rotations per second – it's not that easy to increase capacity, as the drive head can only seek so fast. Still, HP and Seagate expect to release a 146GB 15k drive next year.

Another evolutionary step will be the introduction of high throughput SAS. Currently, SAS maxes out at three gigabits per second of throughput. SATA runs at half that speed. Next year, SAS is expected to double to 6Gbits/sec.

These new 300GB 10k drives will be the basis for that, said Daley. While they won't be 6Gbits natively, much of what is found in these new drives will be reused in drives that support the 6Gbit interfaces.