The long wait is over. Microsoft promised Windows Server 2008 R2 SP1 before the end of Q1 2011 and RTM is now formally announced:
Technet/MSDN availability on February 16th
Public availability on February 22nd
Service Pack 1 includes many security updates as well as a bunch of hotfixes which made installing Hyper-V a task that had to be done carefully. With everything included this will save a lot of time.
SP1 also enables enhanced support for how Failover Clustering works with storage that is not visible for all cluster nodes. In SP1, improvements have been made to the Cluster Validation and multiple Failover Cluster Manager wizards to allow workloads to use disks that are shared between a subset of cluster nodes.
There are already many blogs explaining the two most important new features for Hyper-V:
Specifically for Hyper-V it is now possible to control whether NUMA spanning is allowed. If a VM uses memory from more than one NUMA node, performance will suffer. Hyper-V will try to minimize spanning but if there is no other way it will use memory from more than 1 NUMA node. If you want to avoid this at all times just switch off NUMA spanning in the Hyper-V settings of the Hyper-V server. Of course this is more likely to occur with guests that demand a lot of memory. Now that we have dynamic memory it is also more likely that memory is used from multiple NUMA nodes.
J.C. Hornbeck has collected a number of sources on SP1 improvements:
System Center Virtual Machine Manager 2008 R2 SP1 will follow in 30 days after SP1 RTM. So expect it before the end of April 2011
I will not repeat all this but show SP1 in a few pictures: