[4883] in linux-scsi channel archive
Re: dual-attached disk
daemon@ATHENA.MIT.EDU (Eric Youngdale)
Wed Oct 14 05:59:22 1998
Date: Wed, 14 Oct 1998 00:44:03 -0400 (EDT)
From: Eric Youngdale <eric@andante.jic.com>
To: "George E. Lass" <George.Lass@osc.com>
cc: thoth@purplefrog.com, linux-scsi@vger.rutgers.edu
In-Reply-To: <3623A672.725A9D40@osc.com>
On Tue, 13 Oct 1998, George E. Lass wrote:
> thoth@purplefrog.com wrote:
> I've tried this with the 2.0.30 kernel (RedHat 4.2) and the AHA-2940U
> host
> adapters and it doesn't work very well.
Doesn't surprise me at all that it doesn't work well.
> It seems like if the system that does *not* have the drive mounted is
> reset, it will get into some sort of "reset war" on the SCSI bus with
> the other system. This happend before control is ever passed to the
> boot loader. (must be something in the AHA-2940 BIOS).
Currently there is no support whatsoever for configurations like
this. I don't have a lot of experience with using dual-hosted disks -
the SCSI specification does allow for "reservations" so that one host can
block others from using a device for some period of time, but I have no
idea whether this is usable in practice.
My gut feel is that at a minimum you would need to disable error
handling for the device in question to avoid the reset war issue. Even
then, you have cache coherency issues that would arise if both hosts were
trying to modify the same partition at the same time.
-Eric
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