----- Chris Hoogendyk <hoogendyk AT bio.umass DOT edu> wrote:
> 
> 
> Chris Hoogendyk wrote:
> >
> >
> > Brandon Metcalf wrote:
> >> I am currently using the following default settings:
> >>
> >>   dumpcycle 4 weeks
> >>   runspercycle 20
> >>   tapecycle 25 tapes
> >>
> >> If wanted to, say, have an 8 week dumpcycle could I simply add and 
> >> label 25 tapes and change the parameters above to
> >>
> >>   dumpcycle 8 weeks
> >>   runspercycle 40
> >>   tapecycle 50 tapes
> >>
> >> and expect Amanda to do the right thing?
> >
> > Short answer: Yes. Of course.
> >
> > A bit more: You can change your configuration and then feed it a few 
> > more tapes at a time until you reach your full number of tapes. As 
> > long as it has a new labeled tape each time it wants one, it will 
> > continue to work. When you run out of new labeled tapes, then there 
> > need to be enough tapes that there will be an old one that can be 
> > re-used. Typically, you have a few more tapes than specified in 
> > tapecycle. If runtapes is greater than 1, then you need more --  see: 
> > http://wiki.zmanda.com/index.php/Tapecycle.
> 
> I want to amend my comments with one caveat.
> 
> While Amanda will do "the right thing," to some extent it will be 
> hamstrung by your configuration. You will typically only have one full 
> backup at a time (within a dumpcycle). You will have the constant threat 
> of having a full for some DLE overwritten, and the incrementals that 
> relate to that full becoming meaningless, before you have another full. 
> In addition, a single tape failure can result in multiple DLE's not 
> being recoverable.
> 
> If you changed your original scheme to
> 
>    dumpcycle 2 weeks
>    runspercycle 10
>    tapecycle 25 tapes
> 
> Then you would always have a full backup, and often two.
> 
> If you add 25 tapes and make your new scheme
> 
>    dumpcycle 4 weeks
>    runspercycle 20
>    tapecycle 50 tapes
> 
> Then, again, you will always have a full backup.
> 
> I don't know if your intention in stretching out the tapecycle is to 
> have more coverage, or whether you have too much data for your 
> network/server/tapes to handle in the shorter cycle. I would be 
> concerned about redundancy. If you aren't having trouble with too much 
> data, I would use a scheme like
> 
>    dumpcycle 1 week
>    runspercycle 5
>    tapecycle 50 tapes
> 
> or, perhaps, 2, 10 and 50.

My motivation behind asking the question was to have more coverage.  I 
certainly don't have a problem with too much data as I'm using virtual tapes on 
a large NAS RAID array.  I was thinking that by increasing the number of tapes 
and the dumpcycle and runspercycle parameters, I could recover further back in 
time.  It sounds like this may not be the case which is probably due to my lack 
of understand of exactly how Amanda uses these parameters in its algorithms.

Assuming that I don't have a issue with too much data and I would like the 
following to happen

  * a full backup once per week
  * backups 6 days per week
  * the ability to go back a couple of months

Would a config like the following work?

  dumpcycle 1 week
  runspercycle 6
  tapecycle 75

And could I simply add all of the virtual tapes and once and change the above 
parameters and be OK?

Thanks for the help.

Brandon