*BSD News Article 95162


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From: sthaug@nethelp.no (Steinar Haug)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Socket drivers for SCSI
Date: 12 May 1997 08:02:29 GMT
Organization: Nethelp Consulting, Trondheim, Norway
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In-reply-to: Jason Marshall's message of Sat, 10 May 1997 19:08:43 +0900
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[Jason Marshall]

| > > A long time ago on a free Unix far far away, some folks bantered about
| > > plugging two or more machines together on the same SCSI chain, and
| > > thereby achieving networking of great speed.  And I was wondering if
| > > FreeBSD had such a thing (I am lacking the experience to code such a
| > > beast myself, though I am a programmer).
| > 
| > One of the fathers of {386,Free}BSD's SCSI code, Peter Dufault, once
| > wrote me that he attempted to implement this idea.  I'm not sure
| > whether he ever got it to success.  The biggest point, transfer speed,
| > is now probably already moot due to the invention of 100 Mbit/s
| > ethernet technology.  (And i think you can use a crossover cable to
| > connect just two machines, saving the costs of the hub.)
| 
| But Ethernet has some nasty contention problems that I assume (hope?)
| SCSI does not.  Isn't it easier to guarantee QOS on SCSI than on
| ethernet? (assuming I am trying to do semi-realtime distributed
| computing over the medium).  

Ethernet doesn't have contention problems if you run full duplex point
to point links.

Frankly, I don't understand why anybody would want to use SCSI for high
speed networking - it was never meant for that! If you really, *really*
need QOS in your networks today, buy ATM. Otherwise, 100 Mbps Ethernet
is certainly the way to go (simpler and less expensive - current best
price is around $340 for full duplex NIC + switch port).

If 100 Mbps full duplex is too slow, you can start thinking about 622
Mbps ATM (available from a few vendors), pre-standard Gigabit Ethernet,
or more exotic technologies like Myrinet or SCI.

Steinar Haug, Nethelp consulting, sthaug@nethelp.no