[3514] in linux-scsi channel archive
Re: [Fwd: 2 HA's on same SCSI BUS]
daemon@ATHENA.MIT.EDU (Kurt Garloff)
Thu Mar 12 03:21:18 1998
Date: Thu, 12 Mar 1998 09:03:30 +0100
From: Kurt Garloff <garloff@kg1.ping.de>
To: georgel@osc.com, linux-scsi@vger.rutgers.edu
Mail-Followup-To: georgel@osc.com, linux-scsi@vger.rutgers.edu
In-Reply-To: <35055CE8.477F@osc.com>; from George E. Lass on Tue, Mar 10, 1998 at 09:31:52AM -0600
On Tue, Mar 10, 1998 at 09:31:52AM -0600, George E. Lass wrote:
> Greetings,
> I have a rather interesting challenge ahead.
> I need to build a control system that consists
> of 2 PC's that have *fast* (not NFS) access to
> each other's disk drives. I am considering putting
> 2 host adapters into each PC and then interconnecting
> the HA's for disk access. My configuration would look
> something like this:
> ...
> Has anyone out there ever tried anything like
> this using LINUX & PC hardware? I know it is
> possible to put multiple HA's on a SCSI BUS 'cause
> I've seen it done on a Motorola VME UNIX system
> using their MVME327A.
>
> I currently have redhat 4.2 and am using a single
> adaptec AHA2940 with a SEAGATE ST52160N drive.
I had a DC390 and a DC390F in the same PC connected to the same bus. One had
SCSI ID 6 and the other one ID 7. I used this for testing purposes and I had
no problems with this configuration. However, every partition was seen twice
by my Linux box. So I had to take not to use (mount) any partition twice.
Of course you will run into trouble, when you start to mount the same
partitions from two hostadapters. Consider the following situation: Two
processes are writing to the same file. You can easily imagine that this
will end in FS corruption. If you want to avoid this, you have to mount it
read-only from one box. You will still get inconsitent reads, because the
buffer cache will have old contents. I don't know if it's possible to tell
Linux not to use buffer cache for certain devices.
I'd propose another solution: If you got moderately recent hardware (two
Pentiums) then intall 100MBit Ethernet cards (PCI) and use NFS. (You can also
experiment with CodaFS or SMBFS.) The advantage is, that you get proper file
locking and everything is consistent. NFS bandwidth over 100MB Ether should
be almost as fast as two connected SCSI boxes.
--
Kurt Garloff, Dortmund
<K.Garloff@ping.de>
PGP key on http://student.physik.uni-dortmund.de/homepages/garloff
-
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@vger.rutgers.edu
