A while ago I became aware of some bugs to do with NetWorker probe based backups. While they worked without issue in 7.6 SP1, it turned out that in 7.6 SP2 and 7.6 SP3, an issue was introduced which prevented them from working as desired.
A probe backup typically runs with the following logic:
- Execute command on client
- Does client exit indicating a backup is required?
- If yes: Run backup
- If no: Don’t run backup
All fairly straight forward. Unfortunately, for all of 7.6 SP2 and 7.6 SP3 (base), the probe logic on the server would mistakenly trigger a new backup every time the probe was run. I.e., it wasn’t properly detecting whether the client returns the “no backup required” signal.
This would likely have gone unnoticed in a lot of environments using probe backups, since common uses include:
- Backing up and cleaning up database log files;
- Initiating a once-daily backup in response to a particular condition being met, with short-term probe windows.
However, if your probe was designed to run multiple times during the day and you only wanted one backup, you got a different result.
I’d noticed this behaviour for a while, but never got around to investigating it. So, ironically, when I finally logged a case with EMC about it, I was told that 7.6.3.1 would be out shortly and would resolve the issue. Which, it did.
So, if you’re using probe based backups and you’re currently on either 7.6 SP2 or 7.6 SP3, and the correct behaviour of those probes is important, you need to jump across to 7.6 SP3 CR1 (otherwise known as 7.6.3.1).
Note: The incorrect probe behaviour is actually dictated here by the NetWorker server, not the client.