Mark Abene wrote:
>
> Does amanda know that it should reuse tapes
> that have plenty of space left on them, as opposed to clobbering a tape that
> is full, but still technically marked as reuseable?
>
AMANDA _will_ reuse the tape when its run has come. AMANDA rotates the
tapes one after the other and keeps track of it. When a tape has been
written, it will have to wait its turn to be used again. Even if there
were very few data written on that tape, AMANDA will not ask for it
before its turn has come again. To put it another way, AMANDA does not
append the images of *different* run on a tape alredy written in a
previous run, unless the turn of this tape has come, in which case it is
overwritten. This is an intended behaviour. Trying to append to an
already used tape is very problematic, due to all the different
implementations in the hardware. You risk losing data. So AMANDA will
just require the next tape, not a previous one, each time she runs anew.
AMANDA tries to balance the load over the tapes. If she runs already for
some dumpcycles and your systen does not change very rapidly, then you
should see that all the tapes are more or less used to the same extend
(if this is not the case, then either your system changes too
erratically, or there are entries in your disklist that are
significantly larger than the majority of the rest). This is what
"balancing the backup load over the dumpcycle and over the tapes" means.
If, under these circumstances, you see that there remains plenty of
space unused on your tapes, then you can safely reduce the dumpcycle,
leaving all other parameters untouched. This will increase the mean load
on your tapes and result in a better average usage of them. For this to
work well, you have to define your disklist entries so that they will
fit on the tape, leaving enough room for the incrementals even when
there will be more of them on the tape. It is good to define entries of
various sizes (ideally, the sizes should be uniformly distributed
between their min and max), so that AMANDA can combine them well to
utilize the tape better. You see, it's all about combinatorics and
statistics (and I am happy that AMANDA does this for me) :-)
--
Regards
Chris Karakas
Don´t waste your cpu time - crack rc5: http://www.distributed.net
