On Thu, Oct 16, 2003 at 09:23:47AM -0400, Matt Hyclak wrote:
> On Thu, Oct 16, 2003 at 05:58:26PM +0530, Rohit enlightened us:
> > 
> > This is what I understoond by the terms "dumpcycle", "runspercycle" &
> > "tapecycle". Please correct me if I have misunderstood these terms.
> > 
> > dumpcycle 2 weeks:
> > Full backups of all shares will be done once in every 2
> > weeks (or 10 days - excluding weekends (sat/sun))
> >
> 
> Almost. A full backup of each share will be done *at least* once every 2
> weeks. Sometimes amanda will schedule a level 0 sooner if it will help
> balance out tape use.
> 
> > runspercycle 10:
> > amdump runs 10 days a for dumpcycle of 2 weeks (or 10 days dumpcycle)
> > 
> > tapecycle 20 tapes:
> > number of tapes to use per dumpcycle of 2 weeks. 10 tapes X 2 dumpcycles =
> > 20 tapes.
> > 
> > Did I understand this right?

On tapecycle, I think the "technical definition" is how many tapes "minimum",
amanda will use before reusing a tape.  You could certainly have more tapes
in rotation than the "tapecycle" number.  But you can no have fewer.  I rotate
24 tapes but have tapecycle set to 18 (my changer magazines hold 6 tapes, so
it is really 4 magazines vs 3).

An advantage to this scheme may come up if one of my tapes is ever physically
unable to be used.  I don't have to quickly "amlabel" a "new" tape because
the next one in rotation is beyond the 18 tapecycle.

Another factor to consider with "tapecycle" is "runtapes" (default 1), which
is the maximum number of tapes that amanda can use in a single amdump or
amflush.  My amdumps generally fit a single tape.  There are the occasional
huge dumps though.  So I have runtapes set to 2.  Amanda will use a second
tape if necessary, but otherwise will only use a single tape.

My rationale for these settings is that with a dumpcycle of 1 week and a
runspercycle of 6, I wanted at least 3 wks worth of backups (3 dumpcycles)
available.  Normally I have 4 weeks as I rotate enough tapes to meet that
cycle.  However, if any run(s) take multiple tapes, or a tape is damaged,
then I can afford the extra tape usage and still maintain my 3 weeks of
backup availablity

-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
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