On Thu, Dec 23, 2004 at 03:33:24PM +0200, Shai Ayal wrote:
> OK, you can all stop laughing at me calling 80GB Huge. Sorry.
>
> Anyway, we do have a 80/160GB DLT tape. However I do not like it for 2
> reasons:
> 1. Our previous 40/80 DLT tape let us down and the tape got eaten by the
> tape drive at the most critical time.
> 2. Irrespective of the tape reliability, someone has to change the tape
> each day, since a tape changer is clearly way out of our budget. Knowing
> the people here, and me in particular, this won't happen.
>
> This is why a daily disk drive backup is attractive to us. We are
> content with having just 14 days of history. each week we will also do a
> tape backup for off site storage.
>
> As for the strategy -- If I have some (OK, not HUGE) body of data that
> is unchanging by definition, I would like Amanda to do one level 0, and
> then continue with lower levels until this becomes unpractical (i.e.
> sizeof(level 1) ~ sizeof(level 0) ). I would only need to keep the level
> 0 and 14 level 1's to have a 14 days day by day history. This is almost
> what Amanda does, only there is a dumpcycle limit in days. Can this be
> done ?
>
Some unorganized thoughts.
Use 2 configs, they could both be amanda configs or the daily could be
amanda, the second one (to tape) any backup scheme. This is similar to
what I use, Daily and Archive except both of mine go to tape and my Archive
config is used on a sporadic (at best) schedule.
You would have to make sure they do not attempt to run at the same time.
Do you really need a daily backup for both saturday and sunday? I've
elected to do six daily config backups a week. One runs Sat after midnight
to cover friday changes and the next on Mon after midnight to cover both
weekend days. That leaves me from about 6AM Sat to 1AM Mon to do an
archive if I wish.
This will be old had to A-U readers. You don't want to do all your level 0's
then 14 days later redo them. You will probably be reusing the storage medium,
disk or tape. If so, then you are wiping out the last set of level 0's when
you make the new ones. Should something happen during the dump, you may be
left with NO level 0's.
Amanda doesn't want to do all the level 0's at the same time and then level 1's
till the next complete set of level 0's. It was designed specifically to avoid
that scheme. It can be forced into such a scheme, but it is not recommended.
Instead amanda maintains a collection of entities to backup, file-systems,
directory trees, ... These are kept in a file called "disklist" and the
entities are thus called disklist entries (DLEs).
Each DLE can be customized if need be (dumpcycle, priority, ...) but in general
you will specify a global dumpcycle that applies to all DLEs by default. Amanda
then tries to balance the total amount of data backed up during each run. So
some DLEs will get level 0s on Mon, others Tue, ... Depending on the balancing
act, some DLEs will have their level 0s shifted around. But each DLE will get
"at least one" level 0 during any dumpcycle period. By default amanda will then
drop to level 1s and lower depending on the amount of new data. If there is
very little, it will drop to level 2, if more, do another level 1, if a lot more
(say you downloaded several cd's) it might even decide to do another level 0
since it would be nearly the same size as the level 1.
It seems to me that the default scheme would be good for your daily config to
virtual tapes (disk). But don't pick a dumpcycle of 14 and have only 14 vtapes.
Either maintain a lot more vtapes on disk or shorten your dumpcycle a lot.
--
Jon H. LaBadie jon AT jgcomp DOT com
JG Computing
4455 Province Line Road (609) 252-0159
Princeton, NJ 08540-4322 (609) 683-7220 (fax)
|
