I Have the opposite viewpoint. I prefer hardware compression. It allows me to 
offload processing required to the tape drive (instead of my computers) Since 
some of my systems (including the backup server itself) can be slow, this 
actually speeds things up for me. Also, with hardware compression, I know I can 
restore the tape without having to worry about finding the right libraries and 
programs to do the restore. Also (AFAIK) you can't do remote compression with 
samba which I use for about half of my backups.

On the down side, I need more holding disk and I have to guess at my tape 
capacity.

As for both, don't do it. That is a huge waste of cpu and tape.  The first 
compression algorithm will work fine. The second one will waste space with its 
headers and such since it probably won't be able to get the data any smaller 
than the software compression program did.

If you don't believe me, try to zip a gzip file. See if it gets any smaller.

> -----Original Message-----
> From: Kurt Yoder [mailto:kylist AT shcorp DOT com]
> Sent: Thursday, July 03, 2003 11:57 AM
> To: Michael D. Schleif
> Cc: amanda mailing list
> Subject: Re: to compress or not to compress ???
> 
> 
> 
> Michael D. Schleif said:
> > [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?
> 
> I prefer software compression personally:
> 
> -Amanda can make a more accurate estimate of how much tape is
> needed.  So if you know your tape is 20 GB, and your
> software-compressed dump files total 21 GB, you know they won't all
> fit. With hardware compression you just have to guess-timate
> 
> -Less bandwidth consumed if you do your compression on the client
> side (eg, before it comes to the tape server)
> 
> -Less disk space used on your holding disk
> 
> -If you back up to disks instead of tapes, hardware compression is
> not even an option
> 
> 
> The only drawback to software compression that I can see is the
> greater amount of cpu power consumed. For me, this is not really a
> problem, since my backups all happen in the wee hours when no-one is
> on my systems anyway.
> 
> -- 
> Kurt Yoder
> Sport & Health network administrator
> 
>