The �Hyper-V Hypervisor Virtual Processor� and �Hyper-V Hypervisor Root Virtual Processor� counter sets have the same counters. The only difference between the two is the ��Hyper-V Hypervisor Root Virtual Processor� contains counters for only the Root Virtual Processors (VP�s) whereas �Hyper-V Hypervisor Virtual Processor� has counter for all other partitions.

The virtual processor counters are very useful because they help you understand how much guest VM�s are running and where they are running. Unfortunately these counters do suffer from a small amount of clock skew in WS08 Hyper-V but this only slightly reduces their usefulness. We hope to remove the clock skew in future releases. The skew shows up in that some� %� counters may exceed 100%. I�ve seen some go as much as 110% depending on the system load. The problem has to do with the fact this counter set uses the clock from the root rather than from the hypervisor as a basis of time. For more on clock skew see (http://blogs.msdn.com/tvoellm/archive/2008/03/20/hyper-v-clocks-lie.aspx).

Virtual Processors (VP) are the unit of execution for a partition and each partition contains one guest virtual machine (VM). For each VP there is a set of counters. Perfmon.exe will let you view the counters separately or as an average for all VP�s called �_Total�. VP counters are prefixed with the name of the partition like this �WS08 Guest 1:� followed by the VP id like this �Hv VP 0�. This makes it easy to identify which VP�s go with which partitions.