No 1U, two-socket rack server bests Apple's Xserve in its price range. No two-socket Intel desktop can touch the MacBook Pro for its combination of durability, efficiency, expandability, and quiet operation.
But while Apple's top-of-the-line server and desktop put the rest of the pack to shame, they have what some consider to be a showstopper shortcoming: They run OS X. Now, to me, that's a major plus. The rest of the IT universe seems intent on running something else on their x86 servers, and as such, Apple's hardware is rarely on the table when it comes time to build a Windows or Linux server.
Thanks to Parallels, IT can put Apple hardware on its list with greater confidence, because Parallels Server for Mac (which debuts as Version 3.0) opens Xserve and Mac Pro to 64-bit heterogeneous environments, paving the way for server consolidation, security and testing isolation, and high availability, along with most other uses to which you'd normally put virtualization. Parallels Server for Mac uses the extremely efficient, hardware-accelerated virtualization engine proven in its Parallels Desktop product.
Unfortunately, Parallels Server for Mac both retains too much of its desktop heritage and pares off some desktop features that would have been welcome in Server. Its Management Console is only barely competent to manage multiple VMs, and it becomes unwieldy when those VMs are spread across multiple physical servers. Two Parallels Desktop features -- snapshot and direct disk partition access (implemented in Desktop for Apple's Boot Camp boot-to-Windows tool) -- looked ripe for adaptation to Server for Mac.
Parallels Server for Mac claims as its trump card the ability to run OS X Server as a guest of itself, but that turns out to be what Parallels Server for Mac does least well. OS X Server cannot be installed from Parallels Management Console. Users who have been able to kludge their way into a running OS X guest report stability and performance issues that, so far, Parallels has not addressed with either a fix or concrete guidance in its knowledge base or forums. I held this review for over a month to give Parallels a chance to work it out, but it didn't happen. The lack of OS X guest support, stability and compatibility issues with Parallels Management Console, and the absence of storage and resource allocation features that I expect from a server product lend Parallels Server for Mac a beta feel and make its US$999 price tag seem too high by half.
Windows on Xserve
I tested Parallels Server for Mac on an eight-core Apple Xserve with 3TB of Serial ATA hard disk space, Apple's hardware RAID controller, and 8GB of RAM. In this configuration, I was able to run two instances of Windows Server 2008 and a virtual instance of OS X Leopard Server at the same time, allocating 1GB of RAM and 64GB of virtual drive space to each. I might have run one or two more VMs on this hardware, perhaps more if each instance had a fairly narrow workload assigned to it.
Performance is terrific. Running a single instance of Windows Server 2008 as a guest under OS X Leopard Server, Parallels Server for Mac delivers Windows server application performance that is functionally indistinguishable from native (nonvirtualized) operation. I've come to expect this from Parallels, whose Desktop product delivers similarly impressive performance.
I didn't get as much control over that performance as I require from server virtualization. By adjusting the number of virtual CPUs assigned to each guest OS, I was able to crudely balance performance among guest VMs. A single opaque switch in Parallels Management Console claims to optimize overall performance to favor either the host or the guests. I prefer finer-grained resource allocation in the form of weighting, throttling, or caps on CPU utilization.