Apple killed the Xserve RAID a couple of years ago. But the technology that went into the Xserve RAID was too good to let die. So the best of the team and the best of the product went off on their own and started Active Storage. The Active Storage XRAID is designed with all the features of the old Xserve RAID and some new ones to boot.
There are two types of Active Storage XRAIDs. The first is the Active Storage ES, which comes with redundant cooling, power, drives and 2 4gbps fibre channel ports. The ES also allows for up to 16 SATA II drives (currently for up to 16 TeraBytes (TB), allows for SAS expansion and it has an embedded Linux RAID Kernel. There is also the Active Storage XRAID, which comes with everything that the ES has, plus you can use SAS instead of SATA II drive modules, it has 4 4gbps ports (2 per controller) and uses active-active controllers. Both models can go up to 16 TB and both models support expansion of up to 32 TB via SAS.
The Active Storage XRAID has not been approved by Apple for Xsan. I’ve used it in Xsan environments without issue and there is a forum on Xsanity for support for Xsan. Since the technology has debuted it has been gaining adoption and support, but whether Apple will introduce Xsan support has yet to be announced.
Overall, for Direct Attached Storage (DAS) environments the Active Storage XRAID is a great buy. For Xsan environments I’m still up in the air. Personally, I like to use hardware that is supported by my file system vendor (or Open Source project if it is one). But hopefully there will be support soon so that we have options to bring to the table for providing Xsan storage. With or without Xsan though, the Active Storage XRAID is the next evolution to the old product line and a great product to boot. Easy to setup, an iPhone application for monitoring and zippy fast with the lowest latency that I’ve seen for a shelf of storage that has been slung off the side of a Mac OS X computer.