[Bacula-users] too many tapes used for a backup

[<mar...@up...>]

We just finished a large backup (6.63TB) to a mix of LTO3 and LTO4 tapes.

The odd thing is that the job spanned 49(!) tapes:

	46 LTO3
	 3 LTO4

Of those 49(!) tapes, running "query 14" (List Jobs stored for a given
Volume name) for each tape in the job, I find:

	2 LTO4 tapes are shown as containing only the large (6.63TB) job
       42 LTO3 tapes are shown as containing only the large (6.63TB) job

	1 LTO4 tape contains data from 2 jobs (part of the 6.63TB job and
		7.78GB of data from another backup)

	1 LTO3 tape contains data from 2 jobs (part of the 6.63TB job and
		11.85GB from another job))

	1 LTO3 tape contains data from 3 jobs (part of the 6.63TB job and
		382GB from another job and
		11.93GB from another job)

	1 LTO3 tape contains data from 2 jobs (part of the 6.63TB job and
		19.93GB from another job))

I'm not using software compression. Hardware compression is enabled in the
tape library. The SD is configured with a "Maximum File Size" of 5GB.

I don't understand why so many tapes were used for this job. Even with random,
uncompressible data, that media should be able to store over 18TB. Is it
possible that tape shoe-shining is wasting that much media capacity?

Can anyone suggest any ways to look into this further?

Thanks,

Mark