I had some questions regarding tapecycle, and after reading the man
page and the doc (old and new), I think that they fall short on
describing what tapecycle should be set to. The minimum value of
tapecycle is well covered, but not the maximum value, and how
tapecycle should relate to the number of tapes that have been
labeled.
>>From the man page:
tapecycle int
Default: 15 tapes. The number of tapes in the
active tape cycle. This must be at least one
larger than the number of Amanda runs done during a
dump cycle (see the dumpcycle parameter) times the
number of tapes used per run (see the runtapes
parameter).
For instance, if dumpcycle is set to 14 days, one
Amanda run is done every day (Sunday through Satur-
day), and runtapes is set to one, then tapecycle
must be at least 15 (14 days * one run/day * one
tape/run + one tape).
In practice, there should be several extra tapes to
allow for schedule adjustments or disaster recov-
ery.
So what is an "active tape cycle"? That is never defined anywhere.
Although the last sentence is correct and it makes sense, it does not
explain how tapecycle should relate to the actual number of labeled
tapes.
Here is my bad attempt at an improvement, please do not use it verbatim:
You must have at least tapecycle tapes labeled, but you can have
more. By labeling extra tapes, you can allow for schedule
adjustments or disaster recovery. For example, lets say that your
tapecycle is set to 20 and you have 20 labeled tapes. If you
discover that tape #5 that you are about to put in the drive is bad,
your only alternative is to immediately label a new replacement
tape. If tapecycle was 20 and you had 25 labeled tapes, then you
could put tape #6 in the drive and deal with the problem later.
On the other hand, if the number of labeled tapes greatly exceeds
tapecycle, then AMANDA (insert inefficiency issue here).
--
Tom Schutter (mailto:tom AT platte DOT com)
Platte River Associates, Inc. (http://www.platte.com)
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