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Basics – Default pool debugging 101

Posted by Preston on 2009-10-15

Many of us with NetWorker have been in the situation where a backup has started (particularly when it’s for a newly configured group), and instead of going to the pool we want it to go to, it’s goes to the Default pool. For sites using multiple pools, it’s usually the case that no media will be in the Default pool, and hence the backup won’t go anywhere.

In those situations, determining why NetWorker is suddenly requesting media in the Default pool is quite easy. Sometimes however, the answer is not so easy. A media request may come out of the blue, with no server-initiated activities behind it, and nothing may be logged to indicate what is causing the request. It could be that an end-user is attempting to run a backup, or that a backup process that was server initiated has gone awry, restarted, and for some reason targeted the Default pool.

This leads me to what I’d call “Default pool debugging 101” … or “how to save yourself a lot of hair tearing”. I had a customer once who called me and expressed a level of exasperation over having already spent several days off and on chasing down what might be causing the persistent request for “1 writable volume in the Default pool”.

My solution in such situations is simple: if you can’t spot what is going wrong – why NetWorker is asking for the media in the wrong pool, then label a volume into that pool and see what writes to it. In such cases one of three things will typically happen:

  1. The volume will be loaded but then not used because a process requested it, was aborted, and for some reason NetWorker didn’t detect the abort.
  2. The volume will be loaded and written to by a manual backup process, in which case the metadata for the backup can be used to identify who (or what) has sent the data to the wrong pool.
  3. The volume will be loaded and written to by an errant scheduled backup process that experienced some failure “a while ago”, in which case it can be staged, upon completion, to the correct pool.

I’m the first person to jump to the defense of elegant and well considered solutions. Doing the mundane thing of just labeling media into the “incorrect” pool that NetWorker is requesting media for smacks of inelegance or even a pseudo “brute force” approach. However, sometimes the easiest solution is also the best – instead of wasting considerable amounts of time chasing phantoms, why not just cut to the chase in such media situations where the solution isn’t obvious, and let NetWorker tell you where the request is coming from?


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