On Tue, 26 Mar 2002 at 7:53pm, Fernan Aguero wrote
> ii) perhaps the compression is taking place but my tapetype
> definition is wrong? The following definition was taken from the
> FAQ-O-Matic, although it didn't mention the type of cartridge used:
>
> define tapetype HP-SURESTORE-DAT40 {
> comment "just produced by tapetype program"
> length 19560 mbytes
> filemark 1147 kbytes
> speed 2957 kps
> lbl-templ "/usr/local/etc/amanda/normal/HP-DAT.ps"
> }
That's part of your problem. To use hardware compression, you need to lie
to amanda about your tapelength. How much of a lie depends on your data.
You mentioned a fs with lots of gzipped data -- that isn't going to
compress at all. 30000 kbytes may be a good first guess. Yes, if amanda
hits EOT it will note which filesystems didn't make it to tape and ask you
to amflush them (if they fit on the holding disk) or make sure it gets
them the next amdump.
> Maybe I should run tapetype myself with my hw compression settings
> and see if I can get over 20GB of data into the tape?
Nope. tapetype writes random data to the drive, which doesn't compress.
You'll likely get a value smaller than 20GB.
The best method here is to guess your average compression ratio based on
your data, and tweak as necessary.
--
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University
