Hi,

We are using Backup Exec 12.5 Virtual Agent (SP3) to backup our Virtual Machines. The Backup server and Hyper-V hosts are running Windows 2008 Server x64 SP2.
When Backup Exec is backing up a Hyper-V VM it creates a new "Msft Virtual Disk SCSI Disk Device" each time a VM is backed up (It might also create one when it verfies the backup). This results in a very large registry (C:\windows\system32\config\SYSTEM is around 130MB) and when the Hyper V Host machine is rebooted it takes 15 minutes to show the logon screen. During that time the machine is pingable but no other services are accessible. I did some searching on the internet and found this post:
http://social.technet.microsoft.com/Forums/en-US/winserverhyperv/thread/07f406c8-678e-4609-b535-7dc2073ecaa0
Which describes exactly the problem I have.

The HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\DeviceClasses\{53f56307-b6bf-11d0-94f2-00a0c91efb8b} and HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\ENUM\VMBUS registry keys of the Hyper-V host and Backup server contain several thousands of entries causing the delay when the system is rebooted.

Is this a known problem and is there a solution for this problem? As a workaround I currently delete all Msft Virtual Disk SCSI Disk Devices that are not connected.

Regards,
Emiel