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DPM 2007 Tape erase

I'm having some issues with DPM 2007 SP1 and my tape cycle.  How can I tell DPM to erase the tape before it starts its backup?

Currently I have 4 LTO3 "daily" tapes(Mon-Thurs) that I recycle each week. DPM seems to only add the backup data to the tape.  I want it to erase the tape each day and only add the new data.

Does anyone have any ideas?
1 Solution
Thomas RushCommented:
I see you haven't gotten an answer, so I'll take a guess... note, please, that I don't know DPM specifically.

Look for an option in the backup job for "overwrite" or "append".  If set to "append", it probably will always prefer to leave current data on the tape.  If set to "overwrite", it should wipe out what's already there.

Also, check to see if you can set the data retention (or perhaps called "protection") for these jobs.  If you're always overwriting last week's tape, then set the retention for no more than six days (or maybe five, depending on how it counts!).  Likewise, if you are overwriting a tape from a month ago, set retention for three weeks, or 25 days.
As soon as the data on the tapes is expired, you can (manually?) mark the tapes as free.

The tape-expiration is based on the recovery goals you defined in the Protection Group settings. Based on the information in your question, I would set the retention range to 1 up to 6 days. That way the data on tape will be expired by the time you put the tape back in the tapedrive.

To mark the tapes as free, go to the Libraries-tab of the Management-part of the DPM console. After putting the tape in the drive, you might have to do a Fast Inventory. The tape will be displayed as expired, and with a rigght-clock, or through the right pane you can "Mark tape as free". This will not erase or format the tape entirely (which could take a long time, like a full format), but indicates the tape can be used to write data on it. While writing the tape, the tape will be overwritten.
Unfortunately IMO, this is a major shortcoming of DPM vs the more traditional backup products.

When you Modify Protection Group and get to "Specify Long-Term goals", and click the "Customize" button under "Recovery Goals"  If you choose Daily Backups, then the shortest retention time you can choose is "1 week". Basically that means 1 week plus one day needs to transpire before the tape expires and is available to be overwritten.

This is all the more frustrating given the fact that if you choose "Weekly" backups, you can choose a retention range as short as one week.

So far I have only found two workable options if you want to use daily tapes and overwrite them.

Option 1 is to use two sets of daily tapes, and set the retention time to 1 week. That means tapes will be two weeks old by the time you get back to them in the rotation and by then they will  be expired and available for overwriting.

Option 2 is to use the single week rotation you are probably used to with that other executive backup program, but forcibly mark your tape as free each day before the backup runs. This can be done with a DPM management shell script available here:


In my opinion, it is probably simpler to just use two set of daily tapes.

All of my comments pertain to DPM 2010. I am not familiar with the earlier versions.
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