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Date:      Sat, 20 Feb 1999 17:15:34 -0600
From:      David Kelly <dkelly@hiwaay.net>
To:        Greg Black <gjb@comkey.com.au>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: tape drive position 
Message-ID:  <199902202315.RAA86591@nospam.hiwaay.net>
In-Reply-To: Message from Greg Black <gjb@comkey.com.au>  of "Sat, 20 Feb 1999 12:01:16 %2B1000." <19990220020117.4326.qmail@alpha.comkey.com.au> 

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Greg Black writes:
> > The only way I know to ID a compressed tape is to put it 
> > in a DDS drive which doesn't support compression and see what happens. 
> > Same for Irix and FreeBSD.
> 
> One problem with the method is that, on several BSD variants and
> with at least two brands of DDS-1 (no compression) drives, what
> happens is a system lockup.  This is the only thing (apart from
> my own stupidity) that has ever forced me to reboot a BSD system.

Its been a while since I tried it, but believe a 2.2.x system with a 
1st generation Archive DDS the message written to the console suggested 
the block size on tape was 1 byte, and we couldn't handle that.

I too have seen situations where something goes haywire with the tape 
drive. If one were able to issue a selective RESET without resetting 
everything on the SCSI bus, that would get things going again. Usually 
I have external tape drives so power cycling the device solves the 
immediate problem.

Really would like to ID compressed tapes. The compression status 
reported by "mt status" only reports what will be done the next time 
the tape drive starts writting at the begining of a new tape. Otherwise 
compression-capabable tape drives transparently adjust to the 
compression mode of the tape under their heads. Can't flip compression 
modes in mid-tape.

--
David Kelly N4HHE, dkelly@nospam.hiwaay.net
=====================================================================
The human mind ordinarily operates at only ten percent of its
capacity -- the rest is overhead for the operating system.




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