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From: robsch@robkaos.ruhr.de (Robert Schien)
Subject: How to turn off DAT compression
To: freebsd-scsi@freebsd.org
Date: Fri, 30 May 1997 11:38:26 +0200 (MET DST)
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I have an Archive Python DAT drive (28388-XXX.494) and want to turn
off the compression mode. The reason is I get NCR timeout messages
(there is a SC-200 in my P6NP5 system) when I write files to tape
which are highly compressible. BTW, when this happens the DAT
is winded back and forth wildly and data which are on earlier
sessions (or partitions or volumes, I don't know what the correct
term is when you have miltiple parts on a tape) are destroyed. Two DAT tapes I
have were so heavily trashed that the DAT drive refused even to to
erase them. Here are some of the error messages:

May 29 13:46:21 robkaos /kernel: ncr0: have to clear fifos.
May 29 13:46:21 robkaos /kernel: ncr0: restart (fatal error).
May 29 13:46:21 robkaos /kernel: st1: COMMAND FAILED (9 ff) @f0637800.
May 29 13:46:27 robkaos /kernel: ncr0: timeout ccb=f0637800 (skip)
May 29 13:47:24 robkaos /kernel: ncr0: timeout ccb=f0658e00 (skip)
May 29 13:47:25 robkaos /kernel: st1: 5.0 MB/s (200 ns, offset 8)
May 29 13:47:25 robkaos /kernel: sd1: 10.0 MB/s (100 ns, offset 8)
May 29 13:50:29 robkaos /kernel: ncr0: timeout ccb=f0658e00 (skip)
May 29 13:50:30 robkaos /kernel: st1: MEDIUM ERROR asc:3,2 Excessive write errors

BTW, the DAT cartrdges ware brand new (Verbatim).

Robert 

P.S.: The system is -current (2 weeks old).