When we set up our DPM server to use the Azure Backup Vault, the amount of data we were uploading was relatively small. Over time we have increased the amount that we backup to Azure and it led to us hitting a bit of an issue. We ran out of usable space on the drive that stored the DPM application causing it to fail and all online backups failing too!

When setting up the Azure Backup Agent, the recommendation is that the agent requires approximately a scratch disk of about 5% of that being backed up to Azure. This allows the agent to have storage in preparation for the upload. When we initially started using Azure with DPM, the 300GB we had available on the drive was more than adequate for this. Now it seems that this is inadequate and we needed more space for the scratch space.

There were two ways we could add additional space; we could add another drive and span across to it as a pair of dynamic disks, or we could add another drive with the required capacity to store the scratch disk. Both have pros and cons. By spanning, we could use the existing installation, but could run into the same issue again further down the line as our use of Azure backup grew. By adding the additional drive, we had a clean drive that wouldn’t prevent backups from occurring should the scratch space fill the disk, but we need to reinstall the agent. Or did we?

A little research into the issue showed that it was possible to migrate the scratch space without the need to reinstall.

1. Stop the Azure backup agent by opening an elevated command prompt.                          net stop obengine
2.  Once the service has stopped, locate the location of the scratch disk (usually “%programfiles%\Azure Recovery\Microsoft Azure Recovery Services Agent”) and copy the Scratch folder to its new location.
3.  Once the copy has been completed, open the registry editor (regedit.exe). Go to “HKLM\SOFTWARE\Microsoft\Windows Azure Backup\Config” where you will find the key “ScratchLocation”. Modify this key to reflect the new location of the scratch folder.
4. At an elevated command prompt, restart the Azure backup agent.                                      net start obengine

Once the engine has been restarted it will start to use the new location for the scratch disk.