I am under the impression that the automatic space managment for scheduled backups in Windows Server Backup (2012R2) does not delete backup sets created with "backup once".

Is this impression correct?

  • delete backup sets...created by previously running Windows Server Backup, correct? – Twisty Impersonator Nov 8 '18 at 14:21
  • I don't believe that there is a problem with backup once, but there are conditions under which Server Backup will not function. See link. – harrymc Nov 8 '18 at 16:38

Yes,it is correct.In general,Scheduled backup and backup once have different destination path. Automatic Disk usage management feature comes into play when Windows Server Backup detects that the backup target does not have enough space to accommodate the backup while backup is in progress. The way Windows Server Backup creates space for new backup is by shrinking the storage space allocated for snapshots (called diff area). As a result, one or more older snapshots (and hence backup versions corresponding to those snapshots) occupying the diff area that got shrunk get deleted. Before shrinking diff area, WSB determines whether shrinking the diff area can free up the requisite space so the backup can happen. If enough free space can get created, WSB goes ahead with the shrinking and continues with the backup. WSB will not shrink the diff area to less than 1/8 of Target volume size as we do not want to lose all past backups just to accommodate this one. This is why sometimes backup fail with target out of disk space in spite of automatic disk usage management feature in Windows Server Backup.


  • to clarify: I meant using "backup once" with "same options as scheduled backup". The destination path is the same. – kort3x Nov 9 '18 at 13:37

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.