Windows Server 2008 R2 RC is a signal from Microsoft that Server 2008 R2 has hit the home stretch. "It's time to kick tires and evaluate it," Microsoft group product manager Ward Ralston told me during a recent briefing. Microsoft is ready to talk performance, and although the number of performance comparisons I was shown is small, more are on the way. Here's what you need to know about Windows Server 2008 R2 RC.

What's New in the RC
Windows Server 2008 R2 is an ambitious release that dramatically increases the capabilities of the Windows Server lineup. Server 2008 R2 RC includes many new features worth examining.

File Classification Infrastructure. FCI provides an infrastructure for classifying business data by using file labels and properties and the ability to apply policy based on that classification. FCI is managed via the File System Resource Manager (FSRM) and is compatible with Microsoft SharePoint. You can create rules that move or delete files on a schedule-based basis or any other criteria. It's all automatic and is extensible by third parties.

Hyper-V improvements. Microsoft shipped Server 2008 with a prerelease version of its virtualization technology and delivered the final Hyper-V 1.0 later in 2008. (Hyper-V 1.0 is included with Server 2008 SP2, shipped to customers in May.)

Hyper-V 2.0 includes a long-awaited Live Migration feature. In RC, logical processor support is changed: Hyper-V 2.0 can utilize up to 64 logical processors of the 256 that are available to the host R2 OS. These logical processors can be distributed as needed among virtual machines (VMs) that are running under Hyper-V. (By comparison, Server 2008 now supports 24 logical processors, up from 16 when it first shipped.)

Microsoft has added a processor compatibility mode for Hyper-V 2.0 Live Migration. Previously, it was only possible to perform Live Migration between servers that were running the same processor family and version (i.e., if one server was running on Intel Core 2 Duo, the other also needed to be running on Intel Core 2 Duo). Now, you can perform Live Migration between servers of the same processor family. Microsoft says it's working to add cross-migration between AMD-and Intel-based servers in a future release.

VM Chimney provides TCP offload support to VMs, letting you map a VM to a physical NIC on the host computer and bypass the virtual interface, improving performance. Although disabled by default, in scenarios such as Microsoft SQL Server backup and restore and Live Migration, VM Chimney provides dramatic improvements, Microsoft says.

Microsoft also added Virtual Machine Queue (VMQ) functionality to RC. It, too, is disabled by default because only Intel currently makes VMQ-enabled hardware. Qualcomm has also announced they're entering this market. With VMQ, you can create a unique virtual network queue and pass network packets from the hypervisor to the VM.

Performance and Scalability Improvements
R2 supports more logical processors—now 256. But it isn't enough to just support processors arbitrarily, Bill Karagounis, the principal group program manager of the Windows Server business group, told me. "We did work around NUMA enhancements, so we're well aware of the underlying hardware and topology of that hardware. This is a critical enhancement for scalability."

I was interested to hear Microsoft's first public revelations about the scaling improvements in R2, which experiences near-linear (1.7 times) scaling when moving from 64 processors to 128 on an OLTP SQL Server workload. And throughput on the FSCT file server workload capacity test improves 32 percent from Server 2008 against R2. (This required Microsoft engineers to change code from the days of NT creator David Cutler. "That was his code," Karagounis said, "and let's just say he paid very close attention to the changes we made.")

R2 reduces power consumption. Karagounis noted that some of these changes were also backported to Server 2008 SP2, so that existing customers see these improvements by updating to SP2.

Timing and Availability
Looking ahead, Microsoft's Ralston confirmed that both Windows 7 and R2 would ship by the end of 2009, and not in 2010 as has been widely reported. "As you suspect, Windows Server 2008 R2 will come out in the second half of this year," Ralston told me. "We'll have more details to discuss as time goes by, but you can expect the RTM and launch in the next couple of months." Note, too, that R2 is a 64-bit only release.

Final Thoughts (For Now)
R2 is a seemingly minor update that, in fact, adds almost as much new functionality as its predecessor. For businesses using Microsoft's volume licensing schemes, R2 comes with the package, so it should be looked at closely, especially for those machines providing virtualization functionality.

That said, Server 2008 R2 might be less compatible with software designed for the previous Server version than a typical R2 release. For this reason, it will require additional testing, but the sheer amount of new functionality in Server 2008 R2 marks this release as a major update worth examining.