Hyper-V Host Reports a Virtual Storage Device Error With Pass-through Disk

Applies to: Microsoft Hyper-V Server 2008 R2Windows Server 2008 R2 DatacenterWindows Server 2008 R2 Enterprise More

Symptoms


Consider the following scenario:

You are hosting a Virtual Machine configured with a SCSI attached Pass-through disk from a Windows Server 2008 R2 Hyper-V Host.

You attempt to monitor the performance of the Pass-through disk from the host OS using the following Performance Monitor Counter:

Hyper-V Virtual Storage Device\Error Count

You observe that the Error Count increases when the guest is booted or the guest is running.

Cause


This behavior occurs because the guest OS sends a SCSI command which is not supported by Hyper-V in this scenario. As a result, the host OS increments the Error Count performance counter. This is expected behavior but it is an unnecessary increment and no corrective action is required.

Resolution


When the virtual machine is using a Pass-through disk, you should monitor the performance of the Pass-through disk from within the guest OS.