I'm at a loss here and wanted to ask for your help.

I take care of the IT infrastructures and backups of some external companies.

This week, I've already had the same issue of no more space on the backup target disk, with two different clients. The Setup for both is as follows:

  • Windows Server 2012 R2

  • Backup via Windows Server Backup, WSB

  • Target is an iSCSI Volume located on a QNAP NAS

  • WSB did not automatically free up any space to continue to Backup before the target volume was full

With the first company, "A", I assumed that the "Automatic Disk Usage Management" just didn't do it's job with deleting the oldest backups to free up space. So I ran the wbadmin delete backup -keepoldest command for 3 times, to delete about 20% of all Backups. No errors thrown.
But even after some days now, the space is not getting freed on the NAS.

Now I'm in the same place with Company B, having 720 Backups in store. I ran wbadmin delete backup -KeepVersions:690.

This time there's errors, paraphrasing (sorry, the original is in German):
"Do you want to delete the entry from the catalog" -> Yes -> "Error while deleting Backup 12/25/2016-11:00: The media type is invalid".
However, the WSB GUI shows the amount of backups reduced by the desired amount.

Does anyone have experience the issue of running out of disk space using iSCSI? Is there a way to make WSB reliably free up space as needed - or rather free up space at all? Any pointers?

Your help is much appreciated!

Best regards,

  • 1
    have you seen this? : community.spiceworks.com/topic/… – batistuta09 Oct 15 '18 at 14:12
  • Yes, it was a missunderstanding that I should see any space getting freed on the NAS - the configured iSCSI Volume will always take up 100% of the QNAP disks. However, as chkdsk /F showed and fixed many problems on these disks. WSB now sees the Volume again as online; it still won't run the next scheduled backup though – Kumi Oct 22 '18 at 7:07

With a thin-provisioned iSCSI LUN, the NAS stores all disk blocks that have ever been written to. Deleting data on the volume doesn't change anything as deleting is done on the file system which the block storage underneath doesn't know a thing about.

You need to either "rethin" the LUN (usually by migrating it) or dump iSCSI and use an SMB share. The better solution is to upgrade your storage to provide sufficient space plus some reserve.

  • Thank you Zac, you're right. There was a missconception about volumes on iSCSI drives there. – Kumi Oct 22 '18 at 7:10
  • @Kumi Please don't forget to accept the answer if it is helpful (and maybe vote). – Zac67 Oct 22 '18 at 16:43

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