On Tue, Jul 25, 2006 at 02:06:35PM -0400, Ross Vandegrift wrote:
> On Tue, Jul 25, 2006 at 11:42:12AM -0400, Joshua Baker-LePain wrote:
> > Look at the various bump* options in amanda.conf -- they control when 
> > amanda bumps an incremental up a level.  Theoretically it can go to 9 
> > (just like the backup tools), but there's an increasingly high requirement 
> > for backup image size savings to do the bumps.
> 
> Is there such a limit in Amanda anywhere?

In planner.c there is code deciding upon level that basically
says "if I'm thinking of doing level 9, don't even consider anything
higher, return level 9 as the decision".

And in lots of other code, like reports, cleanup, amadmin, ...
there are things like "for (level = 0; level <= 9; level++)".

> 
> For example, dump from Linux's e2fstools support arbitrary integers as
> dump levels.  From the manpage:
> 
> "A level number above 0, incremental backup, tells dump to copy all files
> new  or  modified  since  the last dump of a lower level. The default level
> is  9.  Historically only  levels  0 to 9 were usable in dump, this
> version is able to understand any integer  as  a  dump level."
> 
> My Amandas don't ever get above a 6, and my predecessor's bump
> settings limited runs to level 3, so I'm not saying level 897125
> backups are a good idea ::-)

My take from your questions is that you want or expect to get high
incremental levels.  Your needs may differ of course, but I'm happy
that my incrementals seldom even get to level 3.  It reduces the
number of tapes needed for a recovery and changed data often appears
in multiple incrementals at the same level for redundancy.

If the capacity of your archive media were limiting, I can see that
the redundancy I appreciate might be a burden.  Amanda does have
parameters to control how aggressively amanda raises the incremental
level.  All but one begin with "bump".  Perhaps very important for
your need might be bumpdays which defaults to "2 days".  This is the
minimum number of dumps at each incremental level before amanda will
bump to the next level.  Dropping it to 1 is a good first step.

Other "bump" parameters affect how much smaller the next level must
be before bumping is done.  If a level 2 is going to be 5.1 MB and
staying at level 1 would be 5.5 MB, is there much sense in bumping.

The non-"bump" parameter affecting these levels is dumpcycle.
If you don't have a long dumpcycle, amanda will never get to high
incremental levels.

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