Subject: Re: connecting multiple machines to a single SCSI disk ?
To: Netbsd Mailing List <netbsd@vu.com>
From: Curt Sampson <curt@portal.ca>
List: port-i386
Date: 12/08/1995 16:03:23
On Fri, 8 Dec 1995, Netbsd Mailing List wrote:

> i would like to connect a number of Pentiums running NetBSD together
> using a single SCSI disk.
> 
> ie.
> 
> machine
> with disk   diskless    diskless    diskless
> --------    --------    --------    --------
>     |           |          |           |
>     +-----------+----------+-----------+
> 
> provided i kept the SCSI cable length within a reasonable length, is such
> a thing possible?

This connection should work just fine, assuming that you've set
all of the controller cards to different SCSI IDs. The machine with
the highest ID (7, usually) will have priority on the bus, priority
descends with the SCSI ID.

> could i have each machine boot and run from a seperate
> partition on the single SCSI disk?

This is rather more difficult. You can't have more than one disklabel
on a disk, and all of the machines will want to mount root from
sd0a and swap from sd0b, unless you modify the kernel. You might
be able to do three machines with root/swap on sd0a/sd0b, sd0e/sd0f,
and sd0g/sd0h if you compile separate kernels for each. You can't
use sd0c/sd0d because these are generally used for the NetBSD
portion of the disk and the whole disk respectively (or is it the
other way around?). You also *must* make sure that no machine writes
to a partition in use by another machine, or disaster will certainly
result!

cjs

Curt Sampson    curt@portal.ca		Info at http://www.portal.ca/
Internet Portal Services, Inc.	
Vancouver, BC   (604) 257-9400		De gustibus, aut bene aut nihil.