On Monday 02 June 2003 10:40, Gene Heskett wrote: > If you then had to recover, you would need only the last 'dumpcycle' > tapes. Note that I didn't say 7 though, because you might be running > a 5 day a week runspercycle, so that would be only the last 5 tapes.
Ok. Thanks - this just clicked for me. > One would use the capacity the makers says it has when the compression > is turned off. Software is the prefered method, for 2 reasons. My tapes say 40* - 80* GB (* = compressed). This is a DLT 8000 drive. This means that I have a 20GB capacity uncompressed? (Just to clarify.) The 40 - 80 GB means I can get between 2 to 4 times the storage with compression on? > 1. gzip can normally outcompress the hardware compressors in most > drives. Night before last, the disklist and dumpcycle positioning > was such that I put something over 10 gigs on a 4 gig DDS2 tape. Of > course I don't do that every nite :) > > 2. amanda counts bytes sent to the tape. If the hardware compression > is on, then amanda has no clear view of the tapes capacity and will > happily write till it hits EOT if you are feeding it already > compressed files, like a whole dir full of rpm's or tar.bz2's, which > will probably grow some in the compressor. So you have to set the > tapetype to something less than the makers propaganda claims & then > (optionally, I've not been able to prove its effective) sacrifice a > chicken. If its turned off, then amanda has a pretty good view of > what the tape can hold and will fill it reliably to 95+% without ever > hitting the tapes EOT. > > There is an amtapetype utility in the distribution that can test that > for you. But start it early in the day, it takes a while to run. I have already decided to use software compression (esp. for reason #2 above). I will have to compile the distro from the Amanda site as the Debian packages must not contain the amtapetype utility. Thanks for everyone's help. -- Brendon Colby Systems Administrator Midcontinent Communications
