Recently I was involved in a an upgrade project to upgrade a 4 cluster running Windows Hyper V 2008 R2. This involved some preparation since I wanted to pre empt any potential problems by reading as much as possible about upgrading to Service Pack 1
One thing that I had not thought of was the lack of space on the Hyper-visor partition- which incidentally was lacking space since it has a 16 GB pagefile.sys. The only way I successfully managed to reduce the pagefile was to make a registry hack to specifiy the intial and max size of the file.
Please use this command to change the size of the pagefile
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Session Manager\Memory Management\PagingFiles”=”<location> <initial size> <max size>, and I beg you to not to use the wmic method which did not work for me and is unclear.
Another unexpected issue was that after all the upgrades were done, one of the cluster members was not authenticating to the cluster. So I had to evict the node from the cluster and then re add it to the cluster, and this solved the problem.
Cluster validation and integration components upgrades went fine.
Here are some links which I really found clear and useful.
http://thelazyadmin.com/blogs/thelazyadmin/archive/2011/03/17/upgrading-hyper-v-r2-to-sp1.aspx
Posted by mcaffari 
