SCSI as a network interface

[Alvin Starr]

On Tue, 1 Jun 1999, Melchior wrote:

> On May 31, 1999 Bill Frederickson said:
> 
> >Thanks all for the replies.
> >
> >Perhaps I should have been a little more specific about my intentions.
> >I'm looking for a fast, easy way to network a cluster [Beowulf style] of
> >PC's each of which already  have SCSI controlers in them. When I was
> >reading through the mail messages I saw what I thought was a reference
> >to using the SCSI controler as a means of interconnecting the nodes. So,
> >not being a SCSI expret,  I posted the message in hopes that maybe this
> >might be a possible way of doing it.  I was hoping to avoid the adtional
> >cost of NIC cards, switches, etc.
> >
> >Any thoughts, and/or suggestions would be most appreciated.
> >
> >Thanks in advance.
> >
> >Bill
> 
> 
> SCSI is not really suitable for direct network connection.  Each SCSI bus
> needs to be terminated at both ends within the same machine.  Given that
> network cards are cheap nowadays (hubs too), the path of least resistance
> is to put in some thirty dollar NE 2000 compatibles.  If you don't want to
> spend
> (as little as) a hundred dollars per hub, you can use 10 base 2 (coaxial
> network
> cable and tees).  The downside is that your network will only run at 10 MBs,
> but it's very cheap and performance will suffice to test many of the
> concepts
> in a smaller array.  If you decide in the future that you need more
> bandwidth
> inside the cluster the cards can be replaced with 10/100 cards and you only
> have to throw out a couple of hundred dollars worth of stuff.

SCSI is distance limited but it does not have to be in a single enclosure.
With LVD the limiting distance is 12 meters, not unreasonable for a small
cluster. With a transfer speed of 80Mbytes/sec you could get the
equivilent of 640Mbits/sec. The SCSI protocol even supports host to host
communications so the idea of using it as a interconnect system was
thought of way back.

This is not to say that using SCSI is easy. But it can be used for a high
speed link between systems.

Alvin Starr                   ||   voice: (416)585-9971
Interlink Connectivity        ||   fax:   (416)585-9974
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