A parallel to serial transition is affecting the whole IT in-chassis communications area. System and component vendors have realised that serial communications are faster than parallel communications, serial cables are smaller and longer than parallel ribbons, and serial interconnects are much simpler – meaning fewer pins – than parallel ones. Going down the serial route means higher speed, greater scalability, less cost, better cooling and less space.

• For the PCI bus it means an evolution to PCI Express. • For SCSI it means the development of Serial Attached SCSI or SAS. Seagate, for example, has just announced a line of enterprise-class 2.5 inch drives that will support SAS. • For chip to chip and card to card communications inside a box or chassis, above the bus level, the industry, led by Intel, is developing the Advanced Switching fabric which is also a serial interconnect .

SATA is thus part of a broader parallel to serial transition. It is expected that as hard drives and DVD drives and tape drives adopt the SATA interface then parallel ATA will wither away and be eclipsed. However, like floppy disks and the parallel port, ATA storage devices could be around for several more years. CD drives may never adopt SATA as they are being replaced by DVD drives. Obviously we’ll probably not see SATA-connected floppies!

Drives
The main disk vendors: Seagate; Western Digital; and Maxtor, all support SATA. A problem is that not all PCI motherboards accept SATA drives. They will need different host adapter software and different power supplies. Disk manufacturers are bridging these problems until motherboards with native SATA interfaces are developed, expected to be readily available later this year.

Western Digital has its Caviar Special Edition SATA drive, a 7,200 RPM unit with up to 250GB capacity. There is an 8MB buffer so the emphasis is on data access speed. It has the ability to use legacy ATA power or new SATA power sources. This consumer product is accompanied by the Raptor 10,000 RPM enterprise SATA drive.

Seagate and Intel are offering Serial ATA hard drives for the price of Parallel ATA hard drives with the purchase of eligible Intel Desktop boards by resellers. Seagate claims it makes the industry's only native Serial ATA hard drives, and its Barracuda 7200.7 incorporates the interface. They are available at 80, 120 and 160GB capacity points. Intel is incorporating Serial ATA support into its latest Desktop boards.

Maxtor has a DiamondMax Plus 9 line of SATA disks with capacities of 80, 120, 200 and 250GB. These are available in retail stores. Maxtor positions these as consumer drives, intended for applications such as 3D gaming, video editing, and digital content creation. Installation is easier than with ATA drives because there are no jumper leads to set. The drives can also attach to an existing ATA power connection or to a SATA power source, another example of an ATA-SATA bridging solution. Maxtor also has a serial to parallel bridge offering via a partnership with chip vendor Marvell.

Controllers
Maxtor’s MaXLine Plus II line of SATA drives are RAID ready, which implies server use. Adaptec has announced a SATA RAID controller. The 4-port ATA RAID 2410SA will be available in July this year for £320 and is part of an Adaptec SATA RAID product family.

Alan Wallman, who runs Emulex in the UK, says Emulex and Intel are developing storage processors that support SATA, and Serial Attached SCSI, and Fibre Channel too, all within a single architecture. He cites IDC research from 2002 that suggests serial disk drives are projected to capture 81 percent of the enterprise market by 2006.

Emulex will market the resulting Fibre Channel products, and Intel will market the Serial ATA and SAS products. In other words, Emulex largely exits the commodity drive interconnect product market. Intel is energetically promoting the parallel to serial transition as a vehicle for standardising and commoditising in-chassis interconnects and opening up a new market for its chips.

Customer Benefits
What customers will see as a result of SATA is the ability to get SCSI-class drive speed and reliability for lower prices. Desktop users will see faster disk access, if they replace equal capacity and spin speed ATA drives with SATA drives, and also less tangible benefits such as more reliable PCs and smaller form factor chassis. Typically customers on the desktop will get better systems for the same money as before. Businesses, previously unable to afford SCSI RAID systems, should be able to spend a little more money and get substantially better data protection. SATA is basically good news all round.