"DPM encountered a retryable VSS error" error message when you use System Center Data Protection Manager 2010 or System Center Data Protection Manager 2007 to protect a Hyper-V virtual machine that has Forefront TMG 2010 installed
Microsoft System Center Data Protection Manager 2010
Microsoft System Center Data Protection Manager 2007
Consider the following scenario:
You install Microsoft Forefront Threat Management Gateway (TMG) 2010 Standard Edition on a Hyper-V virtual machine.
You configure Forefront TMG 2010 to use all available space on one disk for Web caching.
You protect this virtual machine by using System Center Data Protection Manager 2010 or System Center Data Protection Manager 2007.
In this scenario, you cannot create recovery points for the protected virtual machine. Additionally, you receive the following error message:
Recovery point creation jobs for Microsoft Hyper-V \Backup Using Saved State\W2K8-R2 on protected_VM have been failing. The number of failed recovery point creation jobs = 1.
If the datasource protected is SharePoint, then click on the Error Details to view the list of databases for which recovery point creation failed. (ID 3114)
DPM encountered a retryable VSS error. (ID 30112 Details: VssError: The writer experienced a transient error. If the backup process is retried, the error may not reoccur. (0x800423F3))
This problem occurs because there is no available space on the disk that is used for Web caching. When there is no available space on the disk, System Center Data Protection Manager cannot create a shadow copy.
To resolve this problem, increase the capacity of the volume that is used for Web caching.
To do this in Forefront TMG 2010, follow these steps:
Click Start, point to Programs, point to Microsoft Forefront TMG, and then click Forefront TMG Management.
In Microsoft Forefront TMG, expand TMGServerName, and then click Web Access Policy.
Under Related Tasks in the details pane, click Configure Web Caching on the Tasks tab.
Click the Cache Drives tab, and then click Configure.
In the Define Cache Drives dialog box, select a drive that has sufficient space. Then, type the cache size that you want in the Maximum cache size (MB) box, click Set, and then click OK.