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Date:      Wed, 15 Dec 1999 10:09:56 +0100
From:      J Wunsch <j@uriah.heep.sax.de>
To:        freebsd-scsi@FreeBSD.ORG
Subject:   Re: filemarks?
Message-ID:  <19991215100956.30691@uriah.heep.sax.de>
In-Reply-To: <19991212223611.A53246@theatre.sax.de>; from Martin Welk on Sun, Dec 12, 1999 at 10:36:11PM %2B0100
References:  <E11wwsG-0001fn-00@rip.psg.com> <19991212082403.A34441@theatre.sax.de> <E11xAe8-0002q1-00@rip.psg.com> <19991212223611.A53246@theatre.sax.de>

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As Martin Welk wrote:

> However, it worked fine, although some of the CD-ROMs I was going to
> use were not ISO compliant, so a friend of mine in Dresden (who
> brought FreeBSD to me and me to FreeBSD) helped me with some kernel
> patch and I was happy again.

Hehe, you know that friend from Dresden?  I do. :-)

Since that time, FreeBSD understands ancient High-Sierra CDs. ;-)

> Usually, there are two filemarks written to the tape, but there are
> devices ``that can only write 1'' (man page for mt, there is furtter
> informations).

Actually, they can all write 2, but on QIC & alike (don't know for the
newer Tandberg MLRs) you cannot go to EOM, then backspace over the
second of the filemarks, and try writing from there -- you'll get a
`write append error'.  I think all other drives can do this, and the
drive in question here was DDS, so it should be able to work with 2
FMs.

Btw., Matt, wouldn't it make sense to automatically turn the driver
into 1 FM mode for any "TANDBERG" drive?  I don't know how their DLTs
are announcing, though...  Anything else they're building is QIC or
upwards compatible, and AFAIK they are the only vendor still producing
QIC drives at all.

And please, default to variable mode for all the larger QIC
drives... :)

Actually, i'd rather see the historical FreeBSD behaviour restored
where the default was variable for any QIC cartridge >= 525, and
512-byte fixed for anything up to QIC-150.  Sure, this requires to
read one block until the drive will announce an actual density, but
this algorithm used to work well in previous versions of FreeBSD, and
you have to spend the time for ``logging in'' the tape once per mount
session anyway, so it doesn't matter.  (This can take a bit of time on
a larger QIC medium, i know.)

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)


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