To put a fine point on the virtues of Windows Server 2008's trimmer physique, consider that I ran the x64 Windows Server 2008 Standard on an Apple MacBook Pro, running as a 64-bit virtual guest under VMware Fusion software virtualization for OS X. Of MacBook Pro's 2GB of RAM, I reserved 512MB for Windows Server 2008. I made just one allowance for Windows Server 2008: I installed it on an off-board 18GB FireWire-powered hard drive. To be honest, that was for me. I wanted a blinky light that showed me how hard Windows Server 2008 was hitting the drive.

The Bottom Line Microsoft Windows Server 2008 Microsoft, microsoft.com/server Very Good  8.5 criteria score weight Management 7 20% Performance 9 20% Scalability 10 20% Features 8 15% Security 9 15% Value 7 10% Cost: Standard: $999 with 5 CALs, $1,199 with 10 CALs. Enterprise: $3,999 with 25 CALs. Datacenter Edition: $2,999. Windows Web Server 2008: $469. Platforms: 32-bit or 64-bit AMD or Intel x86, or Intel Itanium CPU, with minimum speed of 1.4GHz. Memory and disk requirements vary by edition and features. Author’s recommended minimums for Windows Server 2008 Standard are 1GB of server RAM per virtual instance and 40GB of local hard disk for boot and swap. The GUI-less Server Core’s requirements are much lower. Bottom Line: You couldn’t ask for more, or for less. Windows Server 2008’s fine-grained, modular configurability lets you shrink the OS footprint down to virtualization guest-friendly size, and Server Core drops the Windows GUI to dramatically reduce the memory requirements of a virtualized guest. This server OS presents a minimal attack surface for guest and host instances, and generally removes the requirement for add-in server and client security. It isn’t a server in a box, but it’s Microsoft’s richest server OS by far. About our Reviews and Scoring Methodology

What-ux?
Seen from one perspective, Microsoft wants to reach out to and play nice with Linux. Subsystem for Unix Applications (SUA) is bundled with Windows Server 2008 Standard, Enterprise, and Datacenter, and all Windows Server 2008 SKUs can compile and run many open source and commercial x86/x64 operating systems, OS X being a notable exception. Microsoft's decision, albeit one made under legal duress, to publish its proprietary APIs and protocols should make Linux developers and users of freeware Linux distributions ecstatic.

Seen another way, Microsoft has executed Windows Server 2008 in a way that makes commercial Linux far less appealing. In those places where Linux might be seen as a good fit for its performance and small footprint, any Windows Server 2008 SKU, including the painlessly priced Windows Server 2008 Web and the Windows Server Core license that rides along with all Windows Server 2008 SKUs, all but slams the door shut on Linux in a Windows shop; Linux is just an impossible sell in Windows shops. That's not because Microsoft has exerted some evil monopolistic power over the enterprise OS market, but because Microsoft made the IT-friendly technical, licensing, and packaging decisions that leave very few gaps, if any, left to fill.

Many children at your service
The Hyper-V hypervisor (currently beta, due Q3) and virtual machine management tools baked into Windows Server 2008 Standard will go a long way toward taking Microsoft server virtualization beyond a poor man's alternative to VMware. Windows Server 2008 casts off a cumbersome, high-overhead, heavyweight virtual machine manager model in favor of a wafer-thin, host-optimized hypervisor. This does not take away the substantial value that VMware, Virtual Iron, Citrix/XenSource, and other serious virtualization players add to large-scale enterprise operations that might have thousands of virtual instances running at once. But Microsoft's virtualization has three unique advantages: It costs nothing, its administration is integrated into Microsoft's other server management tools, and Windows Server 2008 is the only host OS it needs to support. In that last case, Windows shops derive a serious performance and scalability kick from the fact that Microsoft's virtualization is proprietary.

Relaxed licensing is a huge win for shops that deploy Windows Server 2008. Buy a big, fat, fast x64 server, and you can use one Windows Server license to host as many virtual guest instances as you like on that one server. Each physical server requires its own license, and Microsoft seat licenses still apply across the board, but I can see an eight-socket Opteron server easily pulling the workload of a half rack of very busy two-socket rack servers, or a full rack of similar servers with typical utilization.

Of course, Microsoft virtualization works on Intel Xeon as well, albeit with lower single-server consolidation capacity. (Lest anyone think I'm harping, I'll write about the enormous advantages that Opteron brings to Windows Server 2008 virtualization elsewhere.) Hyper-V leverages AMD and Intel hardware-accelerated virtualization to reduce the overhead of software virtualization to a minimum. I say "reduce" to cover edge cases, but for most uses, Hyper-V makes the overhead of trapping privileged instructions and swapping guest OS instance contexts in software disappear. Plus, Hyper-V is very flexible in its resource allocation, permitting guest instances the privilege of "owning" a peripheral. When you can afford this, the layers devoted to arbitrating access to a single device by multiple virtual guests are bypassed. I/O bandwidth for each virtual machine can approach native performance. This feature favors servers with lots of expansion slots. For existing servers, you can buy a PCI-Express bus extension chassis to create a bank of, say, LAN adapters to give each virtual instance its own card.