[3517] in linux-scsi channel archive
Re: [Fwd: 2 HA's on same SCSI BUS]
daemon@ATHENA.MIT.EDU (Josep M. Blanquer)
Fri Mar 13 08:55:51 1998
Date: Fri, 13 Mar 1998 14:43:02 +0000
From: "Josep M. Blanquer" <blanquer@cast-info.es>
To: georgel@osc.com
CC: linux-scsi@vger.rutgers.edu
George E. Lass wrote:
>
> Subject: 2 HA's on same SCSI BUS
> Date: Mon, 09 Mar 1998 17:29:08 -0600
> From: "George E. Lass" <georgel@osc.com>
> Organization: NTS Communications, Inc.
> Newsgroups: comp.os.linux.hardware
>
> 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:
>
> SCSI BUS 1
> PC1/HA2---->PC2/HA1---->PC2/SCSI_DISK
>
> SCSI BUS 2
> PC2/HA2---->PC1/HA1---->PC1/SCSI_DISK
>
> 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.
As far as the SCSI specs, you can connect in a single
SCSI but as many HA's as SCSI id's available, and even
ONLY having HA's on it. (I mean no disk or tape or any
scsi devices like this).
In fact, some months ago, me and another guy, built a
new Network SCSI subsystem for linux that allowed to
configure a SCSI HA as network devices! We used
AHA1542 boards on a single bus to HTTP, FTP...and also
could share other devices as disk or tapes without
interferencing (SCSI arbitration philosophy :-) )
The last update we have is on 2.1.42 kernel (uups!)
The only thing you have to have in mind if you
want connect multiple HA in the same bus, is the fact
if one of those, have to not only ask for data to
other devices (initiator mode) but also receive data
from another HA (target mode). If a HA has to do the
last option it has to support target mode operation,
and not all HA's can handle it.
Thinking on your configuration, perhaps could be
a good idea that a linux box with a HA could simulate
"fully" a SCSI disc (or SCSI disk array....) allowing
extra data processing before serving the chunks, or
permitting to have any other storing scheme
internally...or even having an SCSI disk that can
do a backup on another media without worrying about it!
Just a black box that is known as a SCSI disk, and also
backups himself in another media like a DAT tape...)
I don't know if there's such a project like this
or even if it would be useful for some kind of
structures. Perhaps that could help you.
> I currently have redhat 4.2 and am using a single
> adaptec AHA2940 with a SEAGATE ST52160N drive.
AHA2940 supports target mode feature.
Hoping that this helps...
Josep M.
-
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@vger.rutgers.edu
