Maxtor has announced that its 500GB SATA 2 drives will ship in volume before the end of the year. Seagate has not yet made a formal announcement about the availability of its SATA 2 and Fibre Channel 500GB drives, but confirmed to Computer Business Review that it is on a very similar schedule to Maxtor.
Between them, Maxtor, Seagate and Hitachi dominate the enterprise disk drive market, and Hitachi first shipped 500GB drives in volume in April this year. In an industry where even a one-month technology lead can be significant, Hitachi chose a different route to market than its rivals – one that gave it a temporary edge which looks set to be overturned.
Increases in disk drive capacity are usually the result of increases in the density at which data is packed onto individual disks or platters. Maxtor and Seagate waited until they could pack 125GB onto each disk, and then both produced 500GB drives each comprising four disks. But Hitachi meanwhile simply used the data density it had at hand, and shipped a drive that consisted of five 100GB disks.
The more disks, the greater the manufacturing cost and power consumption, especially since each disk is fitted with two read-write heads. More disks also means less throughput, because of greater mechanical run-out or deviation from perfect circularity, which results in less accurate tracking of read-write heads, and more need for re-reading of data.
Maxtor said its decision to wait until it was able to pack 125GB onto each disk was based on an engineering judgment of efficiency and cost, and that the coincidence of it and Seagate’s shipping schedules simply reflects the competitiveness of the two companies’ engineering teams. They do not share a common supply of disks.
Maxtor’s SATA 2 500GB drives will ship in desktop and laptop as well as enterprise versions. The enterprise versions will show MTTF of one million hours on a typical 20% to 30% duty cycle, compared to 500,000 hours for the desktop versions. Maxtor says that MTTF – mean time to failure is technically different to MTBF, or mean time between failures.
SATA 2 is informally defined, and is usually describes drives featuring one or more SATA features such as native command queuing, 3Gbit per second throughput, and hot swappability. 3Gbit per second is the maximum potential throughput, but overall drive throughput has not changed, Maxtor said. Some dense, high capacity ATA disks have been running low on throughput headroom, Maxtor said.
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SAS drives are up to twice as fast as SATA 2 drives, because they spin twice as fast at 15,000rpm. SAS drives also feature more sophisticated error recovery and so are less likely to suffer the need to complete RAID rebuilds, Maxtor said.
Although perpendicular recording technology is imminent, all of the big three’s 500GB drives will feature established linear recording technology. Perpendicular recording will deliver much greater disk data densities than linear. Maxtor said it will ship drives using 160GB disks, next year. At four disks per drive, that would make for 640GB per drive.
Maxtor’s ATA disks will include accelerometers and circuitry that will allow the read-write heads to move in sync with any vibrations, so allowing them to track data more successfully and reduce the number of re-reads. This is already standard for SCSI drives, but is new on ATA gear.
