[ Apologies if this appears twice. The first try bounced. --JJ ]
>how do I use hardware compression of the tape drive? I used
>"compress none" in amanda.conf and set up compression for the
>tape with "mt -f /dev/nst0 compression on". But the Amanda mail
>report announced, that there was no compression. ...
That's what I would expect (it's what I see every day). The compression
Amanda reports in the E-mail is what can do with software. It has no
way of knowing how much hardware compression was able to do.
>I've got a tape
>length of 23616 meg (as tapetype said for a compressed 50gig
>OnStream ADR50). ...
Vendors typically assume 50% compression, i.e. if the native
(uncompressed) capacity of a device is 35 GBytes, they will quote a
compressed value of 70 GBytes. So if OnStream says 50 GBytes compressed
and you got 23.616, that's pretty close to half (taking file marks,
inter-record gaps, streaming, astrological positions, etc into account).
When you use hardware compression, you have to lie to Amanda about the
tape length to compensate. Pick a number you think represents the
amount of compression your data will get (I usually use around 30%)
and crank up the tapetype length value by that much.
If you routinely use more than one tape, taper will report in the NOTES
section exactly how much data it wrote before end of tape, which you
can use to adjust the value to match your data.
>Olaf
John R. Jackson, Technical Software Specialist, [EMAIL PROTECTED]
