The recent introduction of external Sata (eSata) technology, has made it possible to connect external disk drives to a server or workstation and access them at the same speed as internal Sata disks.

Moreover, with a maximum transfer rate of 3Gbits/sec, eSata offers up to five times the performance of USB or Firewire alternatives, making it a good choice when it comes to adding extra disk space or taking backups on a small-business server.

However, as yet, few servers or desktop PCs come with an eSata interface built into them. So, to take advantage of the technology you'll need a plug-in controller such as the Adaptec Sata Raid 1225SA,
reviewed here.

Designed to plug into a single-lane (x1) PCI Express slot, the tiny 1225SA comes with replaceable mounting brackets to enable it to be deployed in low-profile rack mount as well as free-standing tower servers. A connector to cable the card to the disk activity light is also built in along with two independent eSata ports each capable of delivering the full 3Gbits/sec throughput.

Two 95cm long cables to connect to external drives are also included in the box together with drivers for use with Windows XP, 2003 and Vista plus others for Red Hat Enterprise Linux (4.0 and 5.0), Suse Linux Enterprise Server (9 and 10) and Novell Netware 6.5.

Installation is no harder than for any other plug-in card. Open up the server or PC, insert the adapter into a free PCI Express slot then power back up and load the hardware driver. You will need to check that you have PCI Express slots before buying the card but, assuming you do, any hard disk or tape drive with an eSata interface can be attached to the adapter, with hot swapping another feature of the Adaptec controller.

Attach two disks and you can also take advantage of the onboard Raid facilities, although the choices are somewhat limited because more than two disks are needed to support the more advanced Raid levels. Just two levels are available on the 1225SA, starting with Raid 0 where data is striped in alternate blocks across the two disks.

Such a setup will help enhance performance but doesnít really add anything in terms of redundancy compared to the default setting where each disk is accessed independently (JBOD or Just a Bunch Of Disks). The other option is Raid 1 where the disks are mirrored, giving 100 per cent redundancy to protect against a drive failure but halving the amount of disk space available.

Once the disks are attached the array can be configured and initialised directly by pressing Ctrl & A when booting the host server/PC. Alternatively you can install the Adaptec Storage Manager Software provided and manage the 1225SA and other Adapter controllers remotely. On a single small-business server, however, there's very little need for any real management once the array has been configured.

Performance will depend on the disks used, but you can expect to get the same throughput as with an internal Sata disk of the same specification. An external disk will, of course, need some form of enclosure and a power supply. We found a variety of 7,200rpm eSata disks available with capacities up to 500GB and a choice of either standalone units or products where two disks are fitted inside one enclosure.