When introduced at the end of 2002, Serial ATA (SATA) disks helped simplify cabling but did little for performance. But now there's the Raptor from Western Digital, the first 10,000rpm SATA drive capable of taking full advantage of the bandwidth offered by the Serial ATA interface.

Externally there's very little to distinguish the 1-inch high Raptor from other drives, apart from a tiny data connector and a similarly miniscule power connector alongside. Special cables are needed for both, but a legacy power connector is also provided for use in existing systems. Data cables normally come with the controller and there's one for each disk. These can be up to a metre in length, more than double the length of parallel ribbon cables, and they're also much slimmer (just seven wires) which helps with installation, maintenance and case airflow.

As well as ordinary controller cards, SATA-based RAID adapters are readily available, but with most you're limited to just four drives per controller compared to 15 with SCSI. As such, SATA drives like the Raptor are for the time being restricted mainly to use in low-end servers and high-end desktops rather than larger enterprise systems.

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The capacity of the Raptor is just 36.7GB, which is another drawback both for servers and desktop PCs. All the more so given that you can now get up to 250GB with modern parallel ATA drives such as the popular Caviar, also from Western Digital. Larger SATA drives are available, but not at 10,000rpm. Moreover, you'll pay twice as much per megabyte for the Raptor compared to an equivalent Caviar, whether parallel or serial. Plus you need to factor in a SATA controller when upgrading; a basic 2-disk Promise SATA adapter costs around £55 excluding VAT. All of which begs the question - why bother in the first place?

The answer is performance, with the first implementation of SATA supporting a bus speed of 150MB/sec per disk compared to just 133MB/sec for the latest parallel ATA implementation. Added to which the 10,000rpm Raptor boasts a 5.2ms average seek time and 8MB of onboard cache, enabling it to make good use of the SATA bandwidth. Of course, other factors affect throughput, such as host processor, memory, type of controller and so on. You can also improve performance by striping data across multiple disks in an array, regardless of the technology involved.

However, we still recorded a transfer rate of 42MB/sec with just one Raptor in a Pentium III-based IBM server, some 30% faster than a 7,200rpm ATA/100 Caviar tested in the same system. On the downside, it falls a long way short of the 63MB/sec achieved with a 15,000rpm Ultra320 SCSI Maxtor Atlas, but then the SCSI disk (and its controller) is over twice the price.

If you think storage speed is holding back your desktop applications then the Raptor could be worth the extra money, and prices are falling all the time. Similarly, if you have an ATA server that's grinding to a halt, an upgrade to Western Digital SATA disks, and perhaps a RAID controller, could be worth considering. For the ultimate in performance and flexibility though, SCSI still holds sway, but it's a lot more expensive.

The first 10,000rpm Serial ATA disk drive, the Western Digital Raptor offers significant performance benefits over parallel ATA drives for power desktop PC users, although it is around twice the price and limited to just 36GB at present. The Raptor is a also good choice for a small server, but SCSI disks, although more expensive, are faster and more flexible and therefore to be preferred for high-end server applications.