[7675] in linux-scsi channel archive
Re: Multi-LUN CD changer simultaneous access problem.
daemon@ATHENA.MIT.EDU (Chiaki Ishikawa)
Mon Dec 13 02:55:41 1999
Date: Mon, 13 Dec 1999 16:48:40 +0900 (JST)
From: Chiaki Ishikawa <Chiaki.Ishikawa@personal-media.co.jp>
Message-Id: <199912130748.QAA12261@sparc18.personal-media.co.jp>
To: ken@kdm.org
Cc: eric@andante.org, linux-scsi@vger.rutgers.edu
In-reply-to: <19991212232906.A25934@panzer.kdm.org> (ken@kdm.org)
X-PMC-CI-e-mail-id: 12062
>FWIW, I solved the LUN-based changer problem in FreeBSD/CAM by adding a
>sort-of scheduler to the CD driver. All CD devices that are part of a
>changer are grouped together, and commands can only be issued to one LUN
>at a time.
It sounds to me a good solution. The choice of time quantum seems also
reasonable.
I am not a kernel hacker, but probably the
checking of data structure to see if there are pending
requests to different LUNs on the same target by traversing the
linked list as mentioned in Eric Youngdale's post
is functionally equivalent to what you describe here.
Alan Cox has been mentioning partial overhaul of SCSI code and so I am
not sure where the fix should go in (and also when).
--
Ishikawa, Chiaki ishikawa@personal-media.co.jp.NoSpam or
(family name, given name) Chiaki.Ishikawa@personal-media.co.jp.NoSpam
Personal Media Corp. ** Remove .NoSpam at the end before use **
Shinagawa, Tokyo, Japan 142-0051
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