When running Symantec Backup Exec 2010 R3 with a Quantum tape drive on Windows Server 2012 R2 with Hyper-V, I discovered a problem when starting Hyper-V guests and/or managing VHDs.

Symptom

When attempting to start a VM, the VM failed to start with an error like this:

‘<VM Name>’ failed to start.

Microsoft Emulated IDE Controller (Instance ID {########-####-####-####-############}): Failed to Power on with Error: ‘A device attached to the system is not functioning.’

Failed to open attachment ‘Drive Letter:\path\Virtual Hard drivers\VMNAME_########-####-####-####-############.vhd’. Error: ‘A device attached to the system is not functioning”VM NAME’ failed to start (Virtual Machine ID ########-####-####-####-############)

‘VM NAME’ Microsoft Emulated IDE Controller (Instance ID {########-####-####-####-############}): Failed to Power on with Error: ‘A device attached to the system is not functioning.’ (0x8007001F) (Virtual Machine ID: ########-####-####-####-############)

‘VM NAME’: Failed to open attachment ‘Drive Letter:\path\Virtual Hard drivers\VMNAME_########-####-####-####-############.vhd’. Error: ‘A device attached to the system is not functioning’ (0x8007001F) (Virtual Machine ID: ########-####-####-####-############)

‘VM NAME’: Failed to open attachment ‘Drive Letter:\path\Virtual Hard drivers\VMNAME_########-####-####-####-############.vhd’. Error: ‘A device attached to the system is not functioning’ (0x8007001F) (Virtual Machine ID: ########-####-####-####-############)

This Microsoft KB article described the symptom: http://support.microsoft.com/kb/2013544.  However, the suggested solution did not solve the problem.

Cause

The KB article describes the cause as follows:

There is a timing issue with FSDepends.sys and with VHDMP.sys. This timing issue occurs when certain backup programs are installed on computers that are running Windows Server 2008. By default, the FSDepends.sys start value in the registry is set to Manual. When any third-party backup software loads its tape device driver, the software can sometimes result in FSDepends.sys and VHDMP.sys not initializing correctly.

Solution

The KB article suggests the following solution:

To work around these problems, FSDepends.sys should be set to a start value of Boot (0x0).

• Navigate the registry to the following key: “HKLM\SYSTEM\CurrentControlSet\Services\FsDepends”

• Under the “FsDepends” key, change REG_DWORD value “Start” from “3” to “0”

The rest of the solution is to also make the same change for the VHDMP key:

• Navigate the registry to the following key: “HKLM\SYSTEM\CurrentControlSet\Services\VHDMP”

• Change the contained REG_DWORD value “Start” from “3” to “0”