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Backup Exec 2012 DLM troubles - any work around for us?

Created: 14 Jan 2013 | 6 comments

We have a backup server with 5x3TB hard drives and 2xLTO 4 tape drives.
That is used to backup 6 servers (not including itself) first to disk, and then duplicating to tape.  We are lucky enough to be able to do a full backup of every server each night.

To save on costs, we went with 5 WD Green HD's, since they are not essential - if they die they die and are cheaply replaced, and we have the backups on tape anyway.  We also didn't bother with RAID as green drives are not designed for that, so they are 5 separate drives.
We have 1 backup job going to each drive (except for 2 servers with a small amount of data on one of them) - I originally let BE choose where to put data, but that turned into a right mess.

We have a problem that one of the servers is quite large so it can only fit 3 whole days onto the 3TB drive.
Ok, so I originally set the overwrite protection on that job to 2 days - but then every Monday there is nothing on the drive since the DLM has wiped it as the backups have gone past the 2 days limit over the week end.

I can't change to 3 days as it will be filled up on the 4th day of backup before being groomed in time.

So now I've set it to 56 hours, meaning part-way through Monday it should get wiped - again not ideal.

What I was hoping for is some way to disable DLM from triggering every 4 hours - I only want it to trigger on a low space alert.
That would allow me to keep at least 1 backup right the way through until the backup on Monday is part-way through - at which point I assume it would clear up the space mid backup to enable it to finish?

Am I right in thinking that's how it works?
If so, is there some setting or registry hack to turn off the scheduled 4 hour grooming?
Or can I get it to not count weekends maybe?

Any help or other suggestions are appreciated - I'm so close to having it working perfectly for us!

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Colin Weaver's picture

DLM should NOT delete the last complete backup set required to restore a given backup selection (unless you have made registry changes.)

As such even if you say keep for 2 days and you go across a weekend, it should keep the Friday set until the Monday night's backup has completed.

Do you know if any registry changes have been implemented on your server to overide the default behaviour of always keeping the last backup?

james morgan's picture

Hm no I haven't made any registry changes as yet, it's a bog standard installation with SP1.

I had actually read that webpage, but thought keeping the chain only related to when you had incrementals and such stopping the related full backup from being deleted.

Maybe something else happened last wk end to cause that then, though it defenitely said all successful on the Friday, and then all I had was 5 empty disks come Monday.

Is there any log kept of what was groomed and when that could shed some light on things?

I'll try it again.



I just realised something, only 1 backup is set to 2 days, the rest are a lot more, even up to 18 days so something else must have happened to wipe the drives over the weekend.
If there is some kind of grooming log that would still be nice.

james morgan's picture

I was just searching the internet for this problem again, and came across my own post haha!

Still having the above problem and it's definitely deleting the last backup on the disk.
Every Monday I come in and the disk where this server backs up to is empty, even though Friday shows a 1.1TB successful job.

Could it possibly be because it's being duplicated to tape, and DLM thinks that because we have a tape copy it's ok to delete it off the disk?

While I haven't touched any registry keys, where are they just to look at? I can't find anything about that.

It's just the backup set to 2 days retention (the only backup going to this disk) that's the problem.

Colin Weaver's picture

Please log a formal suppot Case DLM should not be removing backup sets early - I suspect you have something else going on but whatever it is both you and Symantec need to understand it.

ALiving's picture

Hi James

I'm finding the same problem. Last week I reconfigured the backups to do a D2D2Tape scenario and have noticed the same thing as you.

Yet our other purely disk only storage, no duplication to tape still has backup sets going back to the 28th of June. I have noticed on this storage is that it will delete expired backup sets as it requires space. So this is clearly a duplication to tape issue.

I really want the DLM to leave expired sets until backup exec really needs the space, that way if help desk need to restore a file they can use the disk copy rather than ordering the tape, but I don't want the headache of failed backups due to retention period issues.