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. [EMAIL PROTECTED] | | / 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