Amanda 3.3.4
Hi,
Another long post from me - thanks to anyone who has time to read it.
I've been reading various docs and posts about dumpcycle, runspercycle,
tapecycle, runtapes online, but still can't figure out how I should set
things up for my needs.
I've got:
- ca. 30TB of data to backup
- I'll try to split this into 500GB or 1TB DLE's, but some will be much
easier to leave as 2-4TB DLE's
- I'm fine with a level 0 only every 30 days, especially considering a full
backup will take 8-10 days.
- I've got 1.5TB tapes that hold about 2TB of data with hardware
compression from testing
- my changer holds 35 tapes
I'd like to have the changer always hold a level 0 dump and then the set of
subseuqent incrementals. So it should take about 15-20 tapes for a level 0
of all DLE's, and then the incrementals over a month should easily fit
within 2-4 tapes, judging from experience here. When the next level 0 dump
starts, I'd like amanda to use as many of the remaining 10 or so tapes
before overwriting tapes from the old level 0 dump (overwriting only tapes
of DLE's that have just had a new level 0, of course). (I will periodically
do a level 0 dump to a different tape set for offset archiving)
How do I setup dumpcycle, runspercycle, tapecycle, runtapes to achieve this?
>From the docs, it seems I'd want:
dumpcycle 30 days
runspercycle 15 #15, for running amdump every other day
runtapes 2 # to allow for DLE's that can get up to 4TB
tapecycle 34 # at least (runspercycle + 1) * runtapes - per docs
suggestion
# and leave one extra as a spare
Is this right?
Does this mean that when I run amdump, it will at most write two
tapes-worth of DLE's, and then stop? Then the next run will pick up from
there? I think so, but would like to make sure. I'm used to the manual
paradigm of "run a full backup" and then do incrementals. But this seems
that it will level out to be the same in the end as that?
HOWEVER, I'd rather have runtapes at 3 or 4 to minimize tape waste and make
it less critical to have evenly-sized DLE's, which will be difficult to
maintain. But if runtapes is 3, the recommended value of tapecycle would be
>= 48, more than my # of tapes. But in practice, 35 should still plenty of
tapes to do what I want without overwriting level 0's prematurely. It seems
like tapecycle minimum should be more like '# of tapes per full backup + #
of tapes for incrementals over dumpcycle + 2 * runtapes', plus one or two
as a buffer. The formula in the docs of "(runspercycle + 1) * runtapes"
plays it very safe when you consider many incremental dumps will go to
holding disk and be collected onto one tape periodically.
I was hung-up on thinking that runtapes had to be enough to fill an entire
level 0 dump, but it seems that's the non-amanda way of thinking?
Thanks
-M
