dpm 2010 backing up using child partition errors

[midcuk]

Dear All

We are backing up our hyper-v virtual machines using child partition copy , on a nightly basis at least two fail to create a restore point (always random servers), if you then manually create the points one by one during the day they complete successfully. All other DPM backups work correctly it is just the child partition ones, any ideas how wwe can resolve this.

 

thanks

 

chris

[Bruce123]

Chris - You haven't said what version of Windows Server is hosting your VMs?

 

I have a theory that random failed backups of VMs on DPM 2010 can be related to either network or I/O bottlenecks caused by DPM. Windows 2008 R2 HV seems to be more resilient than 2008 HV.

 

1. Make sure the Hyper-V Host has the latest service pack installed (I know it sounds obvious but DPM 2010 lists various prerequisites for reliable Hyper-V protection and most of them seem to be incorporated into the latest SP).

 

2. Check what other DPM backups are running at the same time. BMR and system State Backups aren't done incrementally; a BMR backup of 50GB can really hammer your network. If you have any BMR/System State backups, try to schedule these so they occur outside your VM backup window. I have scheduled my (only) BMR for 5am (the VMs finish around 2am).

 

3. By default DPM 2010 allows several VM backups to occur simultaneously (seems to be around 3 from my own experiences). This can impose a high network load/disk IO (on DPM and the protected server), which could potentially cause the backups to fail. There is a registry hack to enforce serialized backups (one after the other). I have not tried it myself as (2) worked for me when I experienced a similar problem.

 

On your DPM server:

HKLM\Software\Microsoft\Microsoft Data Protection Manager\2.0\Configuration\MaxAllowedParallelBackups

Set this to DWORD=1

 

Of these 2) and 3) seem look good avenues of investigation (esp. given your observation that the VM backups are successful when done one-by-one during the day).

 

Good luck.

 

Bruce.

Edited May 13, 2012 by Bruce123