Category Archives: Exchange Server 2010

SCDPM: Fail to Modify Disk Allocation after Exchange DAG Switched


Suppose, you have an Exchange 2010 installation with one or more Database Availability Groups with 2 or more servers in each DAG. You setup backup for one of these DAGs using DPM 2010 UR? or newer (incl. 2012 R2 UR2). Later you change active status for protected copy of mailbox database (for example, you switch active copy to another mailbox server). After that, for database copies which status has changed, you’ll receive following error at Review Disk Allocation page at New/Modify protection group master at DPM console:
"The operation failed because the data source VSS component {76fe1ac4-15f7-4bcd-987e-8e1acb462fb7} is missing.
Check to see that the protected data source is installed properly  and the VSS writer service is running.

ID: 915
Details: The operation completed successfully (0x0)”

If you’ll try to add such DB to secondary DPM server, you’ll receive same error at a disk size calculation step.

This problem is known by Microsoft and will not be fixed.

Why does this happen?

DPM stores information about protected resources into tbl_IM_DataSource and tbl_IM_ProtectedObject tables in DPMDB. If you look into ApplicationPath, LogicalPath or PhysicalPath cells, you find an XML-document describing protected resource. Here is one for Exchange mailbox database in DAG: – DAG-node from which database is protected.
MAILDB01 – name of protected DB
Microsoft Exchange Server\Microsoft Information Store\Replica\DAGNODE2 – path to a copy of protected DB at a DAG node which we are protect. Mind “Replica” element of the path – it means we protect passive (not active) copy of DB. In case of active copy, this part of path won’t exist.

When you change status of mailbox database in DAG, the actual LogicalPath changes, but DPM knows nothing about it and keeps an inconsistent data in DPMDB.


There are two workarounds (choose which suits you best):

At DPM side:

  1. Stop protection of problematic DB with retaining its data.
  2. Add the DB back into an appropriate protection group. DPM will update tbl_IM_DataSource and tbl_IM_ProtectedObject tables.
  3. When consistency check completes, you’ll be able to manage allocated disk space for this DB and setup secondary protection for it.

At Exchange side:

  1. Restore active state for problematic DB as it was when you added it into DPM:
    1. If the DB was in an active state – make it active again.
    2. If the DB was in a passive state – make it passive.

If you require so, you can reinstate DB’s state after modifying disk allocation / setup secondary protection – it doesn’t interfere with synchronization / recovery points creation – it just makes impossible to calculate size of a DB.