On Thu, 29 Apr 2004, George Sinclair wrote:

>I've noticed that NetWorker will occasionally fail to report a tape as
>being full and will instead simply list it as 100%. For example, I'm
>running a backup stream to a particular tape, and NetWorker at some
>point requests another tape (same pool, same backup stream). Usually, if
>I go and look in the mount window (GUI), the previous tape will be
>listed as full under %used. Also, if I run something like: mminfo -vq
>'volume=name' - r '%used', it will report 'full'. Makes sense, but
>sometimes this does not happen and the tape instead lists as 100% under
>both mount window and command line output. Strange! The tape must be
>full or NetWorker would not have requested another tape to continue the
>backup on. In fact, I've even tried mounting the tape in the drive,
>removing all the other writable same pool media from the library and
>then trying to run a backup to it, and it just sits there and requests a
>writable tape, so clearly it knows that it can't put any more data on
>there. Why does it not mark the %used field as full?!!!
>
>I should note we are using an older version of NetWorker (6.1.1 on
>Solaris 2.8 server with RedHat storagenode, same version of NetWorker).

The percentage of tape utilized is an estimate. The estimate is based on
the type of media and the compression rating for that media. Since its an
estimate the percentage utilized number can under-report the utilization
of a tape.

The "full" designation means the tape cannot physically hold any more
data. The 100% means that 100% of the ESTIMATED capacity of the tape has
been used, but that does not necessarily mean the tape cannot hold any
additional data. Tapes that are identified as "100%" utilized can still
receive more data if the data compresses better than what the estimated
compression calls for. This will be common in environments where the data
compresses better than the estimated compression rating for the tape
drives.

This is why you should try to avoid removing tapes from your tape library
until they are marked as "full", although there are certainly some good
reasons to remove tapes from a library earlier than that, such as to ship
them off-site.

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