I have a DPM 2012 server (but I've heard the same behaviour happens with DPM 2010) I'm using to backup my environment; it's connected to a single tape drive (no library), so tape rotation is manual.

My backup schedule is:

  • Disk backups everyday at 20:00
  • Tape backups everyday at 23:00
  • Tape retention 1 week

When I inspect a tape after a successful backup, DPM correctly say all recovery points on the tape are going to expire at backup day + 7 days, at (about) 20:00.

The problem is, after 7 days, when that tape is put back into the drive, DPM complains about not having a free tape to use. At 23:00, when it starts the new tape backups. When the old ones on that tape should already have expired three hours before.

The tape backups can instead be completed successfully on the same tape the next day.

To recap:

  • A tape contains some backups; when inspecting the tape, DPM says they are configured to expire the same day at 20:00.
  • At 23:00 DPM can't use the tape because it says it's not free.
  • The next day, backups on that same tape are successful.

Is this some sort of bug, or am I missing something here?
Do by chance DPM tapes expire on a daily basis, instead of at a given time in the day?

  • If your tape backup occurs at 2300, and retention is one week then surely the data will expire on the tape at 2300, rather than 2000? – Dan May 14 '12 at 8:53
  • No, the backup time is 20:00, DPM always send to tape the latest available full backup it has on disk. When viewing the tape contents, DPM correctly says the backups on the tape are going to expire at 20:00. And yet, they don't... – Massimo May 14 '12 at 9:14
  • I hope you find an answer to this, as we're looking at using DPM for the exact same scenario. Perhaps you should try the Microsoft forums? But please do update this question with the answer - if you ever find one :) – pauska May 14 '12 at 9:16

I opened a support call with Microsoft, they confirmed this is a known problem with DPM 2012 (and 2010), and it will be fixed in a coming update scheduled for July.

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