> It seems that the job with spooling enabled can feed the drive at a
> higher speed, but in the the end both jobs had an average write speed
> of 75 MB/s (no spooling) and 77 MB/s (spooling) The compression ratio
> of this backup was ~1.45:1. The spool device is a large RAID5 which is
> able to do seq. reads at ~160 MB/s. BTW: with LTO-3 I was able to
> write to tape with the same speed. I'm not sure what the limiting
> factor is at the moment. Differnt blocksizes didn't change anything.
>
> LTO-4 needs a minimum of 40 MB/s to stream the data continuously to
> tape. I'm still not sure if the drive has to stop very often during
> backup, because there are some dropouts below 40 MB/s (even with
> spooling). On the other hand, the drive has a 128 MB buffer which
> should be able to cache these short dropouts. I'd like to avoid
> spooling because it nearly doubles the time needed for serveral TB.
>
> Therefore I'm still looking for a way to get the number of start/stops
> that a drive needs while writing to tape.
>
> Does anyone know a tool that is able to get this information from the
> drive - in case HP drives do store this information somewhere at all.
>
> Ralf
>
>
I am also interested in this.
I have pretty big full backup (3,2TB) for which I need around 12 LTO-2 tapes
(with hw compression on). I use spooling with max size of 215GB, and
typically spooling (of max size) lasts 2h50min, while despooling lasts
2h40min. Is this normal that spooling lasts longer than actual writing to
the tapes?
I would drop the spooling part, but I'm worried about tape shoe-shining.
(If only bacula can do despooling and start spooling the next chunk of the
same job at the same time.)
Sandi
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