Date: Sat, 6 Jan 1996 14:05:29 +0100 (MET) From: J Wunsch <j@uriah.heep.sax.de> To: freebsd-hackers@freebsd.org (FreeBSD hackers) Subject: Re: A few NITS about SCSI Tapes Message-ID: <199601061305.OAA13148@uriah.heep.sax.de> In-Reply-To: <199601050103.UAA21083@spooky.rwwa.com> from "Robert Withrow" at Jan 4, 96 08:03:23 pm
next in thread | previous in thread | raw e-mail | index | archive | help
As Robert Withrow wrote:
>
> I don't see any way to retension a qic-150 tape with mt. ``mt eom''
> doesn't go to the end, and cating the device to /dev/null is
> problematic when the tape actually *needs* to be retensioned (as
> in you get errors reading...).
I just had to learn that the SCSI-2 standard actually defines a way to
retension a tape. (It's done by the Re-Ten bit of a load operation in
the LOAD UNLOAD command.)
``A re-tension (Re-Ten) bit of one indicates that the medium on the logical
unit shall be correctly tensioned. Implementation of the re-tension function
is device specific.''
Well, this would give us a way to implement it.
What is the suggested timeout for such a command? (I.e., how long do
some SCSI tapes need in order to retension a cartridge?) Is 1800
seconds enough?
If somebody wants to try it, here's the magic:
scsi -s 1800 -f /dev/st0ctl.0 -c "1b 0 0 0 0:b5 v:b1 v:b1 v:b1 0" 0 1 1
^^^^ ^ ^ ^
timeout EOT _________/ | |
Re-Ten ___________/ |
Load _____________/
See the SCSI-2 docs for an explanation of the EOT bit.
--
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. ;-)
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199601061305.OAA13148>