ouch! That�s quite disappointing... :( We had already noticed this kind of behaviour with DDS-* tapes, but we got some progress varying the block size... and yup, I�m really using gzipped data. :S
For AIT-3, however, i thought this hardware compression was something about using lower tape�s phisical-rolling speeds or alikes, but I could never really find anything concrete about the methods... the only one thing I found was they could use "variable block sizes", but that�s all. Again, not many details. Anyway, I�m giving up the idea of compression for now.
If something, I�m noticeing that (at least with -b 10) it becomes (a lot) slower with time, but I guess this would be more of a question to the -performance list.
Add: while writing this message, I remembered to check the 700V�s "Product Specification Manual", and they mention something about dual-partitions, but it seems something that needs to be implemented at driver level, since it includes SCSI commands. In this case, I would need to format the tape as a 2-partition one... any clue about if and/or how that works on FreeBSD?
Thanks again,
Tulio
Gary Corcoran wrote:
Tulio Guimar�es da Silva wrote:
Hello again,
I�m having some trouble putting a Sony SDX-700V SCSI AIT-3 unit to work on FreeBSD 5.3-RELEASE.
...
Besides the speed, hardware compression seems to not being funcional either. I already tried every 4 possible dip switch setting for compression, but I am still not able to transfer a 180GB archive to a (should-be) 260GB medium.
I can't help you with most of your problems, but regarding the "compression"...
I would guess that if you have 180GB to backup, it's not all text. :)
When I last used a tape drive years ago, when writing to a 2GB tape
that would supposedly hold 4GB compressed, I could fit only about 1.9GB
before the tape was full. Turning off hardware compression, I could fit
2GB. The problem was that I was saving already compressed multimedia files,
and the tape drive's "compression" just added overhead and took up more space.
So unless you're backing up text or similar files, don't believe the
marketing hype about getting 2x the amount onto your tapes...
Gary
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