Problem

The synchronization job for one protection group on my DPM 2019 (with MBS) fails and I get the following two warnings:

1. The used disk space on the computer running DPM for the replica of Volume XXX has exceeded the threshold value of 90%, or there is not enough disk space to accommodate the changed data. If you do not allocate more disk space, synchronization jobs may fail. (ID 3100)

   The SC 2019 DPM AC recommends to Allocate more disk space for replica....

2. Synchronization jobs for XXX on YYY have failed. The total number of jobs = 1. The last job failed for the following reason: (ID 3115) DPM is out of disk space for the replica. (ID 58 Details: There is not enough space on the disk (0x80070070))

   The SC 2019 DPM AC recommends to Modify Disk Allocation ....

Using the GUI to allocate more replica space

Both recommended actions from the warnings always result in one of the following errors:

1. DPM could not execute a WMI query. The query either returned an error or an empty result. (ID: 33507)

2. An unexpected internal error occurred in the StorageManager. ID: 40001

Using PowerShell to allocate more replica space

1. Using the Edit-DPMDiskAllocation cmdlet to increase the replica size:

   $pg = Get-DPMProtectionGroup -DpmServerName <DPM_NAME>
   $ds = Get-DPMDatasource -ProtectionGroup $pg[0] # display $pg and select the desired PG
   Edit-DPMDiskAllocation -Datasource $ds -ReplicaSize ($ds.ReplicaSize + 5TB)
   

   always results in the following error:

   Edit-DPMDiskAllocation : DPM could not execute a WMI query. The query either returned an error or an empty result. (ID: 33507)
   Retry the operation.
   At line:3 char:1
   + Edit-DPMDiskAllocation -Datasource $ds -ReplicaSize ($ds.ReplicaS ...
   + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       + CategoryInfo          : NotSpecified: (:) [Edit-DPMDiskAllocation], NonFatalWmiException
       + FullyQualifiedErrorId : WMIFailedToExecuteQuery,Microsoft.Internal.EnterpriseStorage.Dls.UI.Cmdlet.ProtectionCmdLets.ModifyDPMDiskAllocation
   

2. Using the Set-DPMDatasourceDiskAllocation cmdlet to increase the replica size:

   $pg = Get-DPMProtectionGroup -DpmServerName <DPM_NAME>
   $mpg = Get-DPMModifiableProtectionGroup -ProtectionGroup $pg[0] # display $pg and select the desired PG
   $ds = Get-DPMDatasource -ProtectionGroup $mpg
   Mount-DPMRecoveryPoint -Datasource $ds
   Set-DPMDatasourceDiskAllocation -Datasource $ds -ProtectionGroup $mpg -Manual -ReplicaArea ($ds.ReplicaSize + 5TB)
   Set-DPMProtectionGroup -ProtectionGroup $mpg
   Dismount-DPMRecoveryPoint -Datasource $ds
   

   results in the following error:

   Set-DPMProtectionGroup : DPM could not execute a WMI query. The query either returned an error or an empty result. (ID: 33507)
   Retry the operation.
   At line:6 char:1
   + Set-DPMProtectionGroup -ProtectionGroup $mpg
   + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       + CategoryInfo          : NotSpecified: (:) [Set-DPMProtectionGroup], DlsException
       + FullyQualifiedErrorId : WMIFailedToExecuteQuery,Microsoft.Internal.EnterpriseStorage.Dls.UI.Cmdlet.ProtectionCmdLets.CommitProtectionGroup
   

3. Using another approach to increase the replica size in PowerShell (found in this comment):

   $DPM = Connect-DPMServer -DpmServerName <DPM_NAME>
   $pg = Get-DPMProtectionGroup -DpmServerName <DPM_NAME>
   $ds = Get-DPMDatasource -ProtectionGroup $pg[0] # display $pg and select the desired PG
   $DPM.Proxy.ResizeReplica($ds.DatasourceId, ($ds.ReplicaSize + 5TB))
   

   results in this error:

   Exception calling "ResizeReplica" with "2" argument(s): "Invoke method on Object <SOME_WMI_STRING> failed with return value SizeNotSupported"
   At line:4 char:1
   + $DPM.Proxy.ResizeReplica($ds.DatasourceId, ($ds.ReplicaSize + 5TB ...
   + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
       + FullyQualifiedErrorId : NonFatalWmiException
   

Observations

No matter which method I use to try to allocate more replica space, I observe the following:

• There is permanent read activity (4 - 50 MB/s) on the backup storage, but nearly no write activity (99% of the time 0 MB/s)
• The method runs for about 28 minutes and then aborts with one of the described errors

What I have tried so far

• I confirmed that I have enough free space on my backup storage (60% free)
• I confirmed that the replica space for the protection group is indeed full and I have to enlarge it
• I confirmed that the Windows Management Service (Winmgmt) is running
• I confirmed that winmgmt -VerifyRepository returns WMI Repository is consistent
• I confirmed that the Optimize drives service (defragsvc) is set to Manual and is running (reference)
• I looked for the Registry Key HKLM:\SYSTEM\CurrentControlSet\Services\TmFilter\Parameters. Not even the key TmFilter exists on Windows Server 2019 / SC 2019 DPM. I created it, added the value BypassDPMfilter (DWORD (32 Bit)) with data 1, rebooted, but the errors remained¹ (reference)

¹ Actually, the error from the disk space allocation via GUI changed from 1. (WMI error) to 2. (StorageManager). The error from disk space allocation via PowerShell remained the same (WMI error).

Question

How can I successfully allocate more replica disk space on MBS?