Subject: Re: SCSI network
To: der Mouse <mouse@Rodents.Montreal.QC.CA>
From: Eduardo E. Horvath <>
List: tech-kern
Date: 10/01/1999 09:03:53
On Fri, 1 Oct 1999, der Mouse wrote:

> I'm contemplating using SCSI interfaces as a networking medium.  Does
> anyone have any thoughts on where I should look for (a) convincing a
> machine that it should speak on other than ID 7 or (b) convincing a
> machine to respond as if it were a drive, ie, to respond to another
> device on the bus attempting to contact it?  If necessary I'm prepared
> to make the link asymmetric, with one of the hosts distinctly in
> control of what happens, though I'd prefer to avoid that.

I hope I'm stating the obvious, but to do this you will need a HBA driver
that handles target mode, unless you plan to use a third device as an
in-between.  This is not a trivial task and will probably involve a major
rewrite of the current driver.  Target mode and initiator mode are
disjoint, and depending on the hardware it is possible to have a single
controller operate in both initiator and target mode at the same time.

In that sense it might be easier to use fibre channel which already has
support for encapsulated IP, or you could go raw fibre channel.

> Oh, it is also important that both hosts be able to speak to disks on
> the bus.  (Yes, I do intend to make sure they use disjoint subsets of
> the drives present. :-)

That should not be a problem.

> In case this is hardware-dependent, the machines I'm considering doing
> this with are SPARCstations (ELC, 1+, IPX); if necessary I can dedicate
> a Sun-3/60 to it.

I believe it is possible to program those chips in target mode.  You will
most likely need to write a set of target mode scripts for the chip,

Don't let me discourage you though.  Once you have a target mode driver
you can do all sorts of interesting things, such as turn your computer
into a RAID box.

Eduardo Horvath
	"I need to find a pithy new quote." -- me