> -----Original Message----- > On Thursday 19 June 2003 11:51, Ean Kingston wrote: > >I couldn't find this one in the list archives, so here it is. > > > >I'm using 40GB DLT tapes (according to the label). Despite what the > > comment produced says, I used the non-compressed device. I didn't > > give it an estimate for the tapesize. > > > >Writing 256 Mbyte compresseable data: 34 sec > >Writing 256 Mbyte uncompresseable data: 105 sec > >WARNING: Tape drive has hardware compression enabled > >Estimated time to write 2 * 1024 Mbyte: 840 sec = 0 h 14 min > >wrote 1102644 32Kb blocks in 3372 files in 21817 seconds (short > > write) wrote 1101228 32Kb blocks in 6756 files in 29828 seconds > > (short write) define tapetype HP-DLT1e { > > comment "just produced by tapetype prog (hardware compression > > on)" length 34499 mbytes > > filemark 13 kbytes > > speed 1399 kps > >} > > And it appears the hardware compressor being on cost you 5.5 gigs. > The various 'tapetype' programs all use the output of /dev/urandom as > the data source, and the output of /dev/urandom is not compressible, > and will in fact grow by about the percentage you see above in being > passed thru the hardware compressor. > > As others have noted Ean, you can turn it off, but this must be done > for every new tape that's inserted as the recognition phase of the > drive will turn it back on when the tapes are changed. Such info as > how to turn it on/off should be on the drive makers web page. To > your vendor its obviously not a very high priority to obtain that > info for you else he would have fired up a browser and found it on > the spot.
I'm using Solaris and, according to the documentation, it should not be using hardware compression unless I specify the 'compress' device (/dev/rmt/0cn) as opposed to the one I did use (/dev/rmt/0n). If what you say it true there is some way to force HW compression for the tape drive regardless of what the OS wants.