On 2006-05-26 21:35, Matt Ingram wrote:
what is the actual purpose of the estimates? is the estimate very
crucial in amanda's operation ? I've tried the estimate calcsize but
that still seems to be taking forever. Should I be safe trying estimate
server, or could that screw things up ?
Amanda works better with accurate estimates. How accurate they need
to be depends on the situation. If your tapes are usually only 50%
filled, than underestimating the amount to dump with 100% is not too
bad. (Unless doing the dumps takes too long and bothers the people
that work in the morning.)
If however your tape is filled to about 100% on some days, then you
want the estimates to be almost perfect too.
The factor that is important here is the the last imcomplete file/chunk
written on the tape, is rewritten entirely again on the next tape (maybe
to be flushed with amflush). A bad example: your tapes are 4 Gbyte
capacity, and the last file is just over 3 Gbyte. While writing that
file the drive bumps into end of tape. Now you waste 75% of the first
tape, and need to flush this 3 Gbyte file on another tape too.
In this case, Amanda had better adapted the schedule of some other DLE's
and make that a incremental instead of a full, so that all of the dumps
would fit on that tape. This save tape and dumping/taping time.
See also:
http://wiki.zmanda.com/index.php/Filling_a_tape_to_100%25
which describes some other ways/parameters to avoid suffering from these
conditions.
If I do a flush or dump, and nothing gets written to tape, can I simply
change the tapelist so the tape I just tried to dump to can be reused,
or will that screw things up?
If nothing got dumped (or only that incomplete part) then I usually
do (did actually -- my tapes are large enough currently) an "amrmtape"
followed by a "amlabel xxx same-label", followed by a flush (or
sometimes just insert it for the next nightly run witch autoflushed the
holding files too).
--
Paul Bijnens, xplanation Technology Services Tel +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM Fax +32 16 397.512
http://www.xplanation.com/ email: Paul.Bijnens AT xplanation DOT com
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