Hi Managers,
Thanks for all the suggestions/hints/explanations I got.
Being able to write almost 55 GB of data to (a native 40GB tape) showed I
got some compression...
A large part of the responses reminded me to use the correct device, which I
was using: /dev/nrmt1h (the h stands for highest compression level)
Also important is the compression-ratio data dependant: already zipped files
will not be compressed again.
Then the compression ratio: allthough manufracturers like us to believe a
ratio of 2:1 is relevant, I learned from your answers that a ratio of
(about) 1.7:1 is more realistic (also because of the data dependancy)
Furthermore, dr. Tom Blinn pointed me to the scu utility; I quote part of
his reply:
Is this a real Digital branded TZ89 tape drive? That is, when you look
at it with the console firmware, with the "file" command, or with the
"scu" utility, does the device firmware identify the model as exactly
a match to the "dynamic device recognition" (DDR) database? If so, then
the "h" or "m" device names (but not the "a" or "l" names) for the tape
drive (e.g., /dev/rmt<n>h) should turn on hardware compression. If the
device does NOT match any entry in the DDR database, then you might not
get the right control commands sent to the tape unit to enable hardware
compression. If that's the case, you need to update the DDR database to
identify the correct commands (which you have to discover yourself by
reading the vendor hardware technical documentation). (A Compaq TZ89
will also work; it's the "unsupported" stuff that sometimes doesn't.)
After getting rid of a couple of large, old (compressed) files, I'm able to
write about 62GB to tape, which I'm quite satisfied with.
Thanx again!
Regards,
Alex Harkema
Received on Mon Jan 22 2001 - 07:51:31 NZDT