Michael D. Schleif wrote:

[1] Should I use hardware compression?

There seem to be several schools of thought here.  I want to know how
Amanda works with hardware compression?  What are the advantages of
using software compression?  What are the disadvantages of using *both*
hardware and software compression?

See Kurt's answer.  May I add that using both hardware compression
and software compression at the same time  actually lowers the
capacity of your tapedrive (a DAT-tape, you said).
If you blindly impose the compression algorithm on an already
compressed data will enlarge that data.  Now much depends on the
algorithm.  DAT-tapes use something from the "compress" family.
Try:
     compress somefile
     cat somefile.Z | compress -v | wc -c

Gzip does much better, by implementing a way to indicate
that next few bytes are not compressed.
     cat somefile.Z | gzip -v | wc -c

The only drive I know without that problem is an LTO1 drive.
see:
  http://groups.yahoo.com/group/amanda-users/message/44455

[2] What are the optimal dumptypes for my situation?

I would go for gnutar, compress client fast, index, record, and
apropriate priority (user-data = higher, system = lower).

--
Paul Bijnens, Xplanation                            Tel  +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM    Fax  +32 16 397.512
http://www.xplanation.com/          email:  Paul.Bijnens AT xplanation DOT com
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