On Tue, Sep 13, 2005 at 03:41:34PM +0100, Rodrigo Ventura enlightened us:
> Hi. There are a couple of parameters on amanda.conf that I can't
> figure out exactly their meaning, even after reading the man pages a
> thousand times:
> 
> - dumpcycle, in days
> - runspercycle, in number of amdumps
> - tapecycle, in number of tapes
> 
> tapecycle is the total number of tapes; only these tapes are rotated,
> right?
> 

Not exactly. tapecycle is the minimum number of tapes that will be used
before any single tape can be overwritten. Many people have a tapecycle less
than the total number of tapes so that if a tape happens to go bad, it
doesn't hold everything up waiting for a new one.

> runspercycle is in how many dumps the whole backup is spread? a
> runspercycle of 4 means that the last 4 tapes contain everything to
> recover the whole system? not sure about this...
> 

runspercycle is the number of times you will run amdump in a dumpcycle. If
you consider a dumpcycle of 1 week (we'll get to that in a minute), you
could have a runspercycle anywhere from 1 to 7. If you run it every day,
it's 7. If you just run on the weekdays, it's 5, etc. This just allows
amanda to plan better if it knows how many more runs there are in the
dumpcycle.

> what is dumpcycle? is this how many days can pass after which a backup
> must exist?
> 

dumpcycle is the *maximum* amount of time that each disklist entry (DLE)
gets a full (level 0) backup. amanda may shuffle things around to make it
all fit better on tape resulting in more than one level 0 in a given
dumpcycle, but you'll always have at least 1. 

> and a problem I have is understanding what happens whenever I skip
> amdump for a couple of days. Because of the dumpcycle, it means that
> next amdump will dump a lot more than usual?
> 

Right, because amanda will have scheduled level 0 dumps for some of your
DLEs. When those dumps are missed, amanda tries to play catch up.

> and let say I just require a weekly backup; if I set dumpcycle to 7
> days and runspercycle of 4, it means that it only takes 4 tapes to
> have a full backup? But I can lag until 7 days.
> 

Depends. We know how often you want to run the dump, but how often do you
actually want level 0 backups done? The way I'm reading this, you just want
a full backup of everything once a week, right?

In that case, you probably want 

dumpcycle 0
runspercycle 1
tapecycle X

dumpcycle 0 in this case tells it to *always* do a level 0, and you run
amanda once each time. Tapecycle is dependent on how many tapes you have.

I hope that explains things better...

Matt

-- 
Matt Hyclak
Department of Mathematics 
Department of Social Work
Ohio University
(740) 593-1263