The Xserve RAID is an external disk storage array with a 3U form factor, which can house up to 14 hot-swappable hard disks. Although it's designed for use with Apple Xserve server products, there's no reason it can't work with non-Apple servers either (Apple has a list of certified non-Apple systems here and there's an excellent Web site here that gives an independent view and a load of useful links).
Our review model weighed an absolute ton, as it came loaded with all the goodies that would fit in. In a full unit there are 14 250GB ATA hard drives, a pair of RAID controllers (each of which handles a bay of seven drives), a pair of power supplies and a pair of removable cooling fan units. The hard disks slot into the front panel, and the rest of the kit is accessible from the back; everything's hot-swappable so you don't have to turn the unit off to swap out a failed PSU or controller card. We tested the top-end unit, by the way there are variants that take four or seven drives too.
The unit has a pair of copper Fibre Channel (FC) interfaces, which can connect either directly to a host or into a Fibre Channel switch if you're a SAN kind of person. Although the FC connections carry the data, device management is handled via the Ethernet ports, of which there is one on board each RAID controller card. We connected the box to an Apple Xserve G5 via the latter's PCI-based Fibre Channel card.
To get started, you connect the device into both the FC network and the Ethernet LAN. By default, the unit is set to obtain its IP address via DHCP, so there was no fiddling with addresses to do on our box. Once we'd connected up the unit, we could run up the RAID Admin utility and organise the disks. The config application is Java-based, so although we initially ran it on the Mac server, we did a lot of the configuration work on a Windows-based PC too. The main screen has an initially empty list of managed devices; when you click "Add System" it scans the network for suitable devices, and on production of the appropriate password, the selected unit is added to the list.
The interface is similar to MacOS X's Server Monitor tool it gives red/yellow/green status indicators for each of the key parameters of the system (network links, FC links and such like) and there's a set of tabbed pages at the bottom of the window where you can switch between views of general info, array configuration, components (RAID cards, cooling modules, etc), FC interface details, LAN details and event log items.
Configuring RAID partitions is simply a case of selecting "Create Array" and choosing how you wish to lay out the disk unit. You have a choice of levels, 0, 1, 3, 5 and 0+1, and you simply select the drives you wish to include in the array you're creating. The device can do the necessary initialisation in the background in order that the partition is immediately available for you to use.
Assuming you're using the unit with a Mac server, as we were, the partitions you create in RAID Admin are immediately available to MacOS though since nothing's formatted at first, you'll get an error message telling you "I found a new volume, but I don't recognise it". All you need to do is fire up the Disk Utility package, which is the widget you use to manage any fixed disk on MacOS X, format the partition, and it's visible. Although the Xserve RAID is effectively two separate collections of seven disks, you can use the Xserve's built-in RAID capabilities to add a further level of RAID outside the box.
You could, for example, create a pair of 7-disk striped volumes in the RAID enclosure using its internal RAID controllers, and then pair these into a single mirrored volume using MacOS's Disk Utility. In fact, this latter step brought the only tiny hiccup in our review when we went to pair up the units in Disk Utility, we had to quit and then relaunch the application before it would let us initialise and mount the new volume.
The Xserve RAID is a typical Apple product; it looks good, is full of features, has excellent capacity and, thanks to cleverly-designed management tools, is simple to use as well.
Don't assume that just because it has an Apple badge the Xserve RAID is an Apple-only unit; so long as you have an appropriate FC adaptor, it's just as happy with non-Apple kit.