The Acuta 4 product is an external RAID solution that's available with either an SATA (4S) or USB 2.0/Firewire interface. We used the SATA version in our testing, because it promised the highest level of performance.

The device includes its own internal power supply, so its SATA host connector draws no power from that computer. Nevertheless, that connection uses a conventional SATA cable. For increased reliability, the company is working on a dual-attached model (two interfaces and two cables) that should be available some time soon.

Although most systems have sported SATA controllers for the past two years, SATA connectors appear primarily on motherboards or disk controllers, and aren't really available to link to external devices. But in the past few months, the industry has moved to support external SATA. Thus, the Acuta 4S ships with a 2 foot long SATA cable, just long enough to permit it to sit next to its host computer - the cable's too short to allow positioning the unit any further away.

Up to four SATA drives must be installed inside the Acuta 4S enclosure: ideally, all drives should be identical. A RAID 1 array requires two drives, and a RAID 5 array needs at least three. An optional hot spare can also be defined, so that it becomes immediately available for use should a defect on any other drive require the array to be rebuilt. To choose a specific RAID implementation, users must manipulate DIP switches on the back of the Acuta 4 enclosure. Unfortunately, migrating between RAID levels isn't supported on this device.

Once the device has been configured and the drives installed, the initialization process begins. After only a short time, we had a functioning RAID array based on the four Western Digital WD360 Raptor drives we installed. The computer detected the device as a new hard drive after reboot, treating the array as a single physical disk. Partitioning and formatting remain the implementer's responsibility. Because of its direct connection to an existing SATA controller, no new drivers were needed.

To monitor this device, a serial cable may be used to attach the Acuta 4 to its host computer. There's also a small display on the front of the device that displays status, and supports device controls. The information reported includes fan rotation speed, case temperature, hard disk firmware settings, and so forth. This display isn't terribly useful, because the device really doesn't offer much by way of configuration settings once the RAID level has been selected. Drive status is also easy to ascertain by observing the two LEDs built into the Acuta 4's front panel.