There is a bug with the way NetWorker 7.5.2 handles ADV_FILE devices in relation to disk evacuation. I.e., in a situation where you use NetWorker 7.5.2 to completely stage all savesets from an ADV_FILE device, the subsequent behaviour of NetWorker is contrary to normal operations.

If following the disk evacuation, either the standard overnight volume/saveset recycling checks are done, or an nsrim -X is explicitly called, before any new savesets are written to the ADV_FILE device, NetWorker will flag the depopulated volume as recyclable. The net result of this is that it will not permit new savesets to be written to the volume until such time as it is relabelled, or flagged as not recyclable.

When a colleague asked me to investigate this for a customer, I honestly thought it had to be some mistake, but I ran up the tests and dutifully confirmed that NetWorker under v7.5.2 was indeed doing it. However, it just didn’t seem right in comparison to previous known NetWorker behaviour, so I stepped my lab server back to 7.4.5, and NetWorker didn’t mangle the volume after it was evacuated. I then stepped up to 7.5.1, and again, NetWorker didn’t mangle the volume after it was evacuated.

This led me to review the cumulative patch cluster notes for 7.5.2.1 – while there’s been a more recent version released, I didn’t have it handy at the time. Nothing was mentioned on the notes that seemed to relate to this issue, but since I’d got the test process down to a <15 minute activity, I replaced the default 7.5.2 install with 7.5.2.1, and re-ran the tests.

Under 7.5.2.1, NetWorker behaved exactly as expected; no matter how many times “nsrim -X” was run after evacuating a disk backup unit volume, NetWorker did not mark the volume in question as recyclable.

My only surmise therefore is that one of the actual documented fixes in the 7.5.2.1 cumulative build, while not explicitly referring to the issue at hand, happened to (as a side-effect), resolve the issue.

To cut a long story short though, I would advise that if you’re backing up to ADV_FILE devices using NetWorker 7.5.2 that you strongly consider moving to 7.5.2 cumulative patch cluster 1 – i.e., 7.5.2.1.

 

Within NetWorker, data (savesets) can go through several stages in its lifecycle. Here’s a simple overview of those stages:

Basic data lifecycle

Basic data lifecycle

The first stage, obviously, is when data is initially being written – the “in progress” stage.

After the backup completes, data enters two stages – a browsable period and a retention period. These periods may have 100% overlap, or they may be distinctly different. For instance, the “standard” browse/retention policies chosen by NetWorker when you create a new client are:

  • Browse period – 1 month
  • Retention period – 1 year

A common mistake people make with NetWorker is to assume that the retention period starts when the browse period finishes; in actual fact, the retention and browse period start at the same time, but the browse period can finish before the retention period. So using that standard setting as an example, the saveset is browsable for the first 1 month of the 12 months that it is retained – it is not the case that the saveset is browsable for 1 month, then retained for another 12.

Once data is no longer within the retention period, and there are no backups that depend on it still within the retention period, data is considered to be recyclable.

When data is recyclable:

  • If it is on tape:
    • The data will remain available until the media is recycled. This will only happen once all the backups on the media is also recyclable, and either the administrator manually recycles the media or NetWorker re-uses it.
  • If it is on a disk backup unit (ADV_FILE) device:
    • The data will be erased from the disk backup unit the next time a volume clean operation is run, or nsrim is run (either as a overnight standard event by NetWorker, or manually via nsrim -X).

This isn’t the “whole picture” for data lifecycle within NetWorker, but it is a good brief overview to give you an idea of how data is managed within the environment.

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