On Tue, Jul 25, 2006 at 09:53:10AM +0200, Sebastian Kösters wrote:
> Thanks!
> 
> That helped me.
> 
> I do the backup only weekdays so i set tapecycle to 14, runspercycle to 5
> and dumpcycle to 7.
> 
> Runtapes is set to 1.
> 
> I use 300GB Vtapes....thats enough for my Backups.
> 

Things are easier to follow when you reply either after
the comments or in line with the comments.

> 
> 
> -----Ursprüngliche Nachricht-----
> Von: owner-amanda-users AT amanda DOT org [mailto:owner-amanda-users AT 
> amanda DOT org] Im
> Auftrag von Jon LaBadie
> Gesendet: Dienstag, 25. Juli 2006 08:34
> An: amanda-users AT amanda DOT org
> Betreff: Re: Question about dumbcycle, tapecycle and runspercycle
> 
> On Tue, Jul 25, 2006 at 07:29:02AM +0200, Sebastian Kösters wrote:
> > Hi!
> > 
> > A short question.
> > 
> > I would like to have the possibility to recover a backup thats 14 Days
> old.
> > 
> > I want to use virtuel tapes and a tape-changer for this.
> > 
> > Every 7 Days Amanda should do a full-backup.
> > 
> > Am i right that i need a tapecycle of 14 a runspercycle of 13 and a
> > dumpcycle of 7?
> > 
> > If not, what must i set at tapecycle, runspercycle and dumpcycle to get
> this
> > work?
> 
> Only one is certain, dumpcycle 7, gives you a level 0 (full) backup
> of each DLE ``at least'' once every 7 days.
> 
> runspercycle is how many times you will have crontab run amdump
> during each dumpcycle.  If you do it once every day, runspercycle
> should be 7.  If only on weekdays, 5, if only Mon, Wed, Fri, 3.
> 
> Your setting of runspercycle 13 would be most unusual.
> With dumpcycle 7, it would suggest twice a day except only once
> on ?tuesdays?
> 
> Lets assume daily runs, even on weekends, so runspercycle 7.
> With dumpcycle 7 that matches my two settings.
> 
> We still can't determine a minimum value for tapecycle without one
> other parameter, runtapes.  This is how many tapes, physical or
> virtual, amanda might use for each run of amdump.  Not how many
> it will use, how many it is allowed to use if needed.  My nightly
> backups generally fit a single tape.  But occassionally it overflows
> to a second.  So I have runtapes 2.
> 
> Now the calculation for tapes needed in the cycle is essentially:
> 
>   # cycles to retain X runspercycle X runtapes
> 
> I wanted 4 or 5 cycles worth of backups (about a month).  That would
> be 5 X 7 X 2 == 70.  But, because I determined that I would not be
> using a second tape except occassionally, I'm comfortable with a
> little more than 1/2 that number, I have a tapecycle of 40.
> 
> If my environment adds a lot more data, or some more clients, either
> I will not be able to retain 5 cycles worth of backups, or I will
> have to add another external disk for more vtapes.
> 
> HTH
> 
> -- 

>From what you have described, your choices of 7,5,14,1
for the four parameters seems appropriate.

That would mean, barring any unexpected problems like
client down, network down, ..., that any 5 consecutive
tapes (corresponding to any 7 day period) should contain
at least one level 0 dump of each of your DLEs.

As you expect to have 14 tapes, that would mean you have
just under 3 weeks worth of backups available.

A recommendation for startup.  When you begin, you will
create a disklist of all your DLEs (disklist entries).
If you create that and start your initial first dump,
every single DLE will have to get a level 0 dump immed-
iately.  Not an ideal situation.  I would suggest that
after creating your disklist, at a '#' to the front of
every line to comment them out.  Before doing your
first amdump, remove the # from about 40% of them,
including at least one from every client.  The second
night remove another 40% and on the third night the rest.
That will give amanda a head start on setting up its
final "balanced" schedule of full and incrementals.

You indicate you use 300GB vtapes.  Each vtape is 300GB?
I.e. 4.2 TB?  Thats a lot of storage.  Or might you mean
your vtapes will be on a 300GB drive?  With 14 of them,
each will be about 20GB.

If the latter, you might also consider if your data will fit.
Basically you need room for all your level 0's backups in
5 vtapes (5 runspercycle) so that will be 100GB of vtape.
Some of that 100GB is also needed for incrementals, how much
depends on how active your systems are.

Assuming the above numbers, I'd estimate your amanda installation
will be capable of backing up 50-70GB of client data.

Of course, if your vtapes are really 300GB, recalculate ;)


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