How to monitor virtual machine disk performance on a Windows Server 2008-based computer that has the Hyper-V role installed

On Windows Server 2008, you can monitor disk performance from inside a virtual machine or from the Hyper-V root partition. When you monitor performance from inside the virtual machine, you only have access to performance counters that are provided by the guest machine. Therefore, utilization counters are only relative to the virtual object that is being monitored. In this case, counters will sometimes report more physical resource usage than actually exists.


For example, the average disk queue length on the guest machine may report too many I/O requests. This means that all the requests are not queued. Some requests are completed and are on their way back to where the performance data is been collected.

On a Hyper-V server, one of the functions of the root partition (Physical Machine) is to provide monitoring information by using both WMI and performance counters. To obtain more accurate information while you monitor disk performance, you can use the Hyper-V root partition performance counters. You can use the following Hyper-V storage objects and counters that are provided by the root partition to monitor disk performance for the virtual machines:

• Hyper-V Virtual IDE Controller objects
  
  • Read Bytes / Sec
  • Write Bytes / Sec
  • Read Sectors / Sec
  • Write Sectors / Sec
• Hyper-V Virtual Storage Device objects
  
  • Error Count
  • Flush Count
  • Read Bytes / Sec
  • Write Bytes / Sec
  • Read Count
  • Write Count

The Hyper-V virtual IDE controller gives details on disk rates and commands. The Hyper-V virtual storage device gives details for virtual storage read and write. If you have integration services installed, you can monitor both IDE and SCSI-emulated disks through the Hyper-V virtual storage counters.