Amanda Backup wrote:
My configuration (2.4.2) has these settings:
dumpcycle 1 weeks
runspercycle6
tapecycle 18 tapes
Does this mean that given a level 0 today, the
next level 0 will be at the latest 1 week from
today?
Exactly. Of course, if the balance of load over the week (i.e. over the
dumpcycle) permits it, you might see level 0s more often.
Or could it mean that within each dump cycle
there will be at least 1 level 0 but that
they could be up to 12 dumps apart (begin
of one cycle, end of next)? That is nearly
what one file system is doing.
Normally, this shouldn't happen. That it happens, it means that the load
is too heavy for this dumpcycle. Now, what does this mean, you will
ask... ;-) It means that the dumpcycle is too short, or the tapes have
too small a capacity and they cannot absorb more data per run. The
easiest solution is to increase dumpcycle to, say, 10 (you can verify
that it is indeed a balancing problem if you do a "amadmin config
balance" and see the projected load and the number of overdue disks).
What AMANDA always tries is to get the load as evenly distributed as
possible over the dumpcycle period, taking into account constraints like
"at least one level 0 every dumpcycle days per disk", priorities,
capacities, previous backup sizes etc. This is a "bin packing problem",
the "bins" being the tapes :-). There is no exact solution to it -
actually, it is a computationally very hard one and the subject of
ongoing academic research. But if you choose your parameters
"reasonably", you will see that AMANDA solves it very well (I am always
amazed by the combinations she uses to "pack" all those levels in one
tape efficiently).
I suggest you start with a somewhat larger dumpcycle than you think is
necessary, say 15 days. Let AMANDA do some dumpcycles this way. You will
get a feeling of the "balanced load" on your tapes, i.e. you will see
that your tapes get *evenly* filled (as long as this is possible of
course), up to a certain percentage. AMANDA will *not* try to fill the
tapes as much as possible because she tries to spread the backups evenly
on the tapes. As soon as you see that you have steadily "room" on your
tapes, that is left empty, you can start decreasing your dumpcycle
carefully. This way you will eventually reach the Optimum :-)
--
Regards
Chris Karakas
Dont waste your cpu time - crack rc5: http://www.distributed.net
