[Action Required] CRITICAL Issue Advice MWA-2017-0001


MWA-2017-0001: Backup Compatibility Issue with Scrub Policies


12.0, 12.1, 12.1u1


An critical issue has been found when using some backup software on file servers on which Moonwalk Agents are installed (discovered with Microsoft’s ‘Windows Server Backup’ component (all versions) - other backup products may also be affected).

Specifically, when Moonwalk stubs are deleted from a backup image or overwritten by subsequent backup runs, a stub deletion/overwrite is detected by the Stub Deletion Monitoring feature which causes the corresponding secondary storage files to become scrubbable. If Moonwalk Scrub Policies are also in use, or are used later, this will lead to the premature removal of secondary storage files resulting in stubs that can no longer be demigrated.


This issue is rated CRITICAL for affected configurations.

If Scrub Policies are in use, data will be lost once the scrub grace period is reached.

Even if Scrub policies are not in use, backup job performance will be impacted due to stub deletion updates. If this issue is not addressed, systems which start using Scrub Policies in the FUTURE may also experience this issue.


Configurations are affected if using a backup product that creates copies of stubs to a local volume or to a file system within a disk image file. Windows Server Backup writes backed up files to a VHDX image file. Bare metal backup software may also do this. Most enterprise backup products write backup data in an alternate archive format rather than storing the original files/stubs ‘as-is’. Such products should NOT be affected by this issue.

It is strongly recommended that even if your configuration is NOT affected, that the ‘ACTIONS REQUIRED’ below are still performed to safeguard against future changes to your backup software and/or configuration.


Perform these steps, strictly in the order given:

  1. [IMMEDIATELY] Disable ALL Scrub tasks
  2. Upgrade to Moonwalk 12.1u2
  3. Run a Post-Restore Revalidate Policy across ALL VOLUMES
  4. Re-enable any Scrub tasks

If you have any queries or concerns, please ensure that you have completed Step 1 above, then contact support@moonwalkinc.com directly.