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Seagate revs up SATA speed

Keep up at the back

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Seagate and AMD have demonstrated a 6Gbit/s link between SATA disks and a server, double the speed of the current SATA 2 spec and the same as the fastest SAS speed.

The justification for the faster speed is to try and keep up with the accelerating growth in capacity - and cache capacity - of SATA disks, now at the 2TB level and destined to double and even triple in the foreseeable future. PC and server processors are also gaining more power through multi-CPU and multi-core technology. Also, SATA-interface solid state drives, such as Intel's X25-M SSD, can use the speed hike to get more I/O to/from the drive.

SATA was first launched in 2002 with a 1.5Gbit/s speed - about 150MB/sec - as a replacement for then current parallel ATA (PATA) interconnect standard between storage devices and servers. Serialising the interconnect provided faster speeds, longer cables (up to 1m) and scope for speed increases in the future.

An external SATA (eSATA) interconnect was introduced in 2004. SATA 2 doubled the speed to to 3Gbit/s - about 300MB/sec - in 2005 and started being required by storage devices, according to Seagate, in 2007.

Each SATA standard is backwards-compatible with the previous one.

In August 2008 the Serial ATA International Organisation (SATA-IO) ratified a 6GBit/s physical layer - delivering about 600MB/sec. AMD and Seagate have now teamed up to demo their prototype technology at either end of a SATA cable.

The idea is to introduce the new faster SATA one to two years before it is actually needed so that products can be developed and the technology bedded down in time for use. Seagate recommends that the interface data rate keeps ahead of the media data rate and so does not throttle back the device. The company reckons that SATA 3 won't be really needed until 2011.

By that time we may be hearing about the next SAS speed jump to 12Gbit/s and SATA 4 may also be just visible on the horizon, a couple of years behind.

Seagate says the general SATA 3 specification "has been enhanced with improved power management (and) advanced data steaming". The new standard may formally be known as SATA Revision 3.0, but will probably just get shortened to SATA 3. ®

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