Last year, I wrote a post about some of the things to look forward to in Windows Server 2008 R2 and, a week or so later, I was able to follow it up with the news that Terminal Services gets a big improvement as it becomes Remote Desktop Services (RDS). Six months have gone by, we’ve had the beta, and now the release candidate is here… and that release candidate has some new features – mostly relating to performance and scalability:

• Looking first at the improvements to Hyper-V (in addition to those in last week’s post on the R2 wave of virtualisation products):
  • There are networking improvements with VM Chimney/TCP Offload capabilities whereby network operations are redirected to the physical NIC (where the NIC supports this), reducing the CPU burden and improving performance. The original version of Hyper-V supported chimney operations in the parent, but virtual machines could not take advantage of the functionality. This helps Hyper-V to scale as 10Gbps Ethernet becomes more common (a Hyper-V host can already saturate a Gigabit Ethernet connection if required) but it’s worth noting that not all applications can benefit from this as it’s more suitable for large file transfers (file servers, etc.) rather than web servers.
  • Another new Hyper-V networking feature is NIC direct memory access (NIC DMA), which shortens the overall path length from a physical NIC queue to virtual machine, resulting in further performance improvements. Because each NIC queue is assigned to a specific virtual NIC there’s still no sharing of memory (so no impact on security isolation) but direct access to virtual machine memory does avoid copies in the VSP and route lookups in the virtual switch; however this feature is disabled by default (as the only real benefit is found with 10Gbps Ethernet and only a few NICs currently have the capability to process it).
  • The long-awaited live migration functionality is definitely in (it was also in pre-release versions of the Hyper-V but was pulled before release). Windows Server 2008 R2’s clustered shared volumes are instrumental to making this feature work well and, even though I don’t believe it’s entirely necessary, VMware have had the functionality for several years now and Microsoft needs to be able to say “me too”.
  • Sadly, another “me too” feature (dynamic memory) has definitely been dropped from the R2 release. I asked Microsoft’s Jeff Woolsey, Principle Group Program Manager for Hyper-V, what the problem was and he responded that memory overcommitment results in a significant performance hit if the memory is fully utilised and that even VMware (whose ESX hypervisor does have this functionality) advises against it’s use in production environments. I can see that it’s not a huge factor in server consolidation exercises, but for VDI scenarios (using the new RDS functionality), it could have made a significant difference in consolidation ratios.
• Away from Hyper-V there are further performance and scalability improvements in the operating system, with support for up to 256 logical CPUs, improved scheduling on NUMA architectures, and support for solid state disks. As well as the power management improvements I mentioned in my original post last October, the operating system uses less memory and networking improvements result in improved file transfer speeds on the LAN, whilst new multi-threaded capabilities in robocopy.exe (using the /mt switch) can provide up to an 800% improvement in WAN file transfers. Putting these improvements into practice, Microsoft told me that one OLTP benchmark for SQL Server showed a 70% improvement by moving from 64 to 128 processors and a file server throughput test showed a 32% improvement just by upgrading the operating system from Windows Server 2008 to Windows Server 2008 R2. Indeed, Microsoft is keen to show off these improvements at TechEd next month (together with System Center products being used to manage and cap power usage) and they will also announce a new power logo as an additional qualification for the Windows Server logo programme. Some of the power improvements will be back-ported to Windows Server 2008 SP2, although that operating system still won’t quite match up to R2.

None of these are big features but they have the potential to make some significant differences in the efficiency of an organisation’s Windows Server estate – an important consideration as economic and environmental pressures affect the way in which we run our IT systems. This isn’t the whole story though as Microsoft still has a few more surprises in this release candidate. With the RC code available to TechNet and MSDN subscribers today, I’m not sure how Microsoft is planning on keeping them quiet but, for now, my lips are sealed so stay tuned for part 2…