On Mon, Feb 24, 2003 at 10:43:12AM -0800, John Oliver wrote:
> The sudden jump in the size of this backup was caused when I moved the
> holdingdisk.  It didn't occur to me that I was moving it on to the
> filesystem I was backing up... :-)  I just added /hold to the exclude
> file.  So, backups will shrink dramatically tonight...

Yeah, that would do it...

> I'm still interested in finding out what the flaw in my understanding of
> how amanda handles compression is, though.  I'm sure it's something
> really obvious that I'm an idiot for not seeing, but I still think my
> tapes should be able to hold more than 20GB when compression is being
> used.

A tape with a raw capacity of 20G can hold no more than 20G of data.
Period.  amanda has nothing to do with this and it cannot be changed
except by buying a tape drive which is capable of (reliably) writing
data to the tape at a higher density than the tape was designed for.

However, the 20G of data that amanda writes is 20G of compressed
data, which will generally expand to substantially more than 20G of
uncompressed data.  The communication problem here appears to be that,
when others on the list are talking about the compressed size of the data,
you're interpreting it as the uncompressed size.