Look harder at the hardware
With that subheading, you expect me to drone on here about the intangible value of build quality, great software and other Apple platform goodness that transforms the same-old, same-old $1,500 to $2,500 Intel rack server into something worth $2,999. Buyers of Intel servers are accustomed to comparison shopping based on hardware specifications and price, so let's stick with hardware. The Woodcrest rack server basics that I detailed in Part 1 are a given. Apple went its own way even in its engineering of those features required to qualify Xserve Xeon to compete in its class. But, except to appreciate that Apple hasn't lost its touch for server engineering, Apple-ness doesn't raise the worth of Xserve Xeon. The direct value that Apple adds to Intel's standard Woodcrest system design is easy to see if you open yourself to the possibility that putting Intel chips in a server needn't define the boundaries of a server's capabilities.
SAS, SATA, and DVD-R DL
Server-attached storage has gotten a bad rap for so long that vendors usually assume that 1U rack servers will use networked or external storage. Many types of server deployments benefit from the simplicity and speed of local storage, and to that end, Apple designed Xserve Xeon with three bays that accept removable Apple Drive Modules. Unlike the Mac Pro workstation, which you can expand with raw SATA drives, Xserve Xeon requires that you buy drives from Apple that are pre-mounted in Drive Modules. Fortunately, Apple's markup for Drive Modules is reasonable--lower than other storage and server vendors with which I'm familiar. With three 750 GB SATA drives, 2.25 TB of local storage, an Xserve Xeon might take on roles you wouldn't ordinarily assign to a standalone server. A giant swath of local disk is a real boon for grid applications.
The value twist that Apple put on Xserve Xeon's removable drives is that each of the drive bays will accept either a SATA or a Serial-Attached SCSI (SAS) Drive Module. These two busses share one backplane physically and, it seems, logically: My Xserve Xeon eval unit shipped with three SATA drives, but the system enumerates them in its hardware inventory as nodes on a tree of SAS/SCSI devices. This is a cozy arrangement; Xserve Xeon's internal drives and Fibre Channel-connected Xserve RAID volumes are all connected to logical SCSI adapters.
If you're willing to sacrifice speed for capacity, SATA is for you. If you can't bear the thought of life without 15,000 RPM drives, go SAS. Boot from SAS and put SATA in the other two bays, boot SATA and have a screaming RAID 0 SAS stripe on bays 2 and 3, whatever you like. With that flexibility, it's much easier to plan for the use of hard drives for backup and portable storage. That strategy is advanced by OS X Server's standard GUI and command-line tools for doing file and folder-level archiving with compression, creating virtual disk images that have compression and/or encryption applied, and creating formatted disk images that are ready to burn to DVD. OS X Server Tiger reduces full-volume imaging and restoration to single operations.
When OS X Leopard ships early next year, Time Machine will make backup continuous and automatic. I'm not sure how Time Machine will operate with removable drives, but given that they're built into Mac Pro and Xserve Xeon, I'm full of ideas.