Basics – Need a different volume from pool …

The scenario:

• A clone or stage operation has aborted (or otherwise failed)
• It has been restarted
• It hangs waiting for a new volume even though there’s a partially written volume available.

This is a relatively easy problem to explain. Let’s first look at the log messages that happens. To generate this error, I started cloning some data to the “Default Clone” pool, with only one volume in the pool, then aborted. Shortly thereafter I tried to run the clone again, and when NetWorker wouldn’t write to the volume I unmounted and remounted it – a common thing that newer administrators will try in this scenario. This is where you’ll hit the following error in the logs:

media notice: Volume `800829L4' ineligible for this operation; Need a different volume
from pool `Default Clone'
media info: Suggest manually labeling a new writable volume for pool 'Default Clone'

So, what’s the cause of this problem? It’s actually relatively easy to explain.

A core component in NetWorker’s media database design is that a saveset can only ever have one instance on a piece of media. This applies as equally to failed as complete saveset instances.

The net result is that this error/situation will occur because it’s meant to – NetWorker doesn’t permit more than one instance of a saveset to appear on the same piece of physical media.

So what do you do when this error comes up?

• If you’re backing up to disk, an aborted saveset should normally be cleared up automatically by NetWorker after the operation is aborted. However, in certain instances this may not be the case. For NetWorker 7.5 vanilla and 7.5.1.1/7.5.1.2, this should be done by expiring the saveset instance – using nsrmm to flag the instance as having an expiry date within a few minutes or seconds. For all other versions of NetWorker, you should just be able to delete the saveset instance.
• When working with tape (virtual or physical), the most recommended approach would be to move on to another tape, or if the instance is the only instance on that tape, relabel the tape. (Some would argue that you can use nsrmm to delete the saveset instance from the tape and then re-attempt the operation, but since NetWorker is so heavily designed to prevent multiple instances of a saveset on a piece of media, I’d strongly recommend against this.)

Overall it’s a fairly simple issue, but knowing how to recognise it lets you resolve it quickly and painlessly.