At its core, Xserve is a two-socket Core microarchitecture Xeon (Woodcrest) rack server. As I wrote in my review, in hardware design, Xserve lives up to market standards. Some touches, like the SAS/SATA drive bays, a PCI-X slot for existing expansion cards and the SuperDrive dual-layer DVD burner, help tip the scale in Xserve’s favor. But the reason to buy Xserve is OS X Server: No other server app platform rivals it, and no other server system runs it. If you want OS X Server, you need a Mac, and Xserve is the only Mac that’s equipped with external drive bays and a baseboard management controller.