I'm looking at a similar problem here. One of the ideas we came up with was
to create a current directory (e.g. /dbdumps/current) which gets backed up
by Amanda. Inside are symlinks to the actual dump files in the daily
directories (/dbdumps/01, /dbdumps/02, ...). Your daily DB dump script
updates the symlinks in current when it is done.

We haven't implemented this yet, but Amanda should dereference the symlinks
and back up the right data. This way you always access the same DLE and get
your normal Amanda behaviour.

In your case, depending on what your dumps look like, you could run diff on
today's and yesterday's  dump and only back up the result (Amanda always
backs up whole files).
In our environment this doesn't really matter though, since the dump files
are changing pretty dramatically at times, so an incremental would look like
a level 0 anyway most of the time.

Personally, I'd feel safer with just backing up the whole dump every day and
leave the job to Amanda.

Your milage may vary of course.

Bernhard

> -----Original Message-----
> From: owner-amanda-users AT amanda DOT org
> [mailto:owner-amanda-users AT amanda DOT org]On Behalf Of mbrkic AT farelogix 
> DOT com
> Sent: Tuesday, March 18, 2003 9:14 AM
> To: amanda-users AT amanda DOT org
> Subject: differential vs incremental backups
>
>
> Hi,
> I have a disk that is a cache for database backups
> and is a set of 30 directories with database exports
> of the last 30 days. I want to use Amanda to backup
> ONLY the latest written directory every night,
> without ever doing a full backup of the whole disk
> (it is too big
> to fit on one tape! :(  )
>
> In other words, is there a way to tell Amanda to
> always back-up only the changes from the last run
> regardless of dump levels. Equivalently, is there a way
> to fool Amanda into thinking that a full backup was
> done every night, after the level 1 completes
> successfully.
>
> Any other ideas would be appreciated!
>
> Cheers,
> Milos
>
>
>