On Thu, Jul 03, 2003 at 11:57:22AM -0400, Kurt Yoder wrote:
> 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

Conversely, if you have a DLE full of something that compresses
down to 20% of its original size, Amanda will know that there's
more room on the tape for other stuff.  With hardware
compression, Amanda won't know that that DLE compresses better
than your other ones.

- Better compression, probably.  Hardware compression is
  typically some variant of LZ, isn't it?  I don't know how
  gzip -1 (the default "compress-fast") compares with that, but
  gzip -9 (the default "compress-best") does a lot better.

  Ok, here's one quickie far-from-representative test.  Sorted in
  order of decreasing size, a largish, mostly-text file, and its
  compression by compress, and by the several grades of gzip.
      Size      CPU     File
      -------   ----    --------------------
      5560320   0       amanda-2.4.4.tar
      2096458   0.88    amanda-2.4.4.tar.Z
      1496904   0.68    amanda-2.4.4.tar.gz1
      1227454   1.28    amanda-2.4.4.tar.gz6
      1220934   2.01    amanda-2.4.4.tar.gz9

  This time, even gzip -1 beat LZ.  I don't know whether that's
  typical.

--

|  | /\
|-_|/  >   Eric Siegerman, Toronto, Ont.        erics AT telepres DOT com
|  |  /
When I came back around from the dark side, there in front of me would
be the landing area where the crew was, and the Earth, all in the view
of my window. I couldn't help but think that there in front of me was
all of humanity, except me.
        - Michael Collins, Apollo 11 Command Module Pilot