[849] in linux-scsi channel archive
Re: SCSI over IP / IP over SCSI
daemon@ATHENA.MIT.EDU (Erik Corry)
Sat Oct 26 11:54:04 1996
To: linux-scsi@vger.rutgers.edu
Date: Sat, 26 Oct 1996 16:52:42 +0100 (MET)
Cc: smurf@smurf.noris.de
Reply-To: erik@arbat.com (Erik Corry)
From: erik@arbat.com (Erik Corry)
Matthias Urlichs:
> We're not trying to reserve anything. Both systems will initally boot from
> /dev/sda (or whatever) via the BIOS. The SCSI standard does say that you're
> not allowed to say "I'm sorry, I'm busy, somebody else is reading right
> now, try again later" (or so I remmeber).
>
> The only way to boot Linux in such an environment is to have an initial
> disk (right now, this has to be a RAM disk (*)) with a linuxrc script which
> figures out your SCSI ID, and sets /proc/sys/kernel/real-root-dev
> appropriately.
>
> (*) The very good reason for the RAM disk requirement is, I'm sure, that
> nobody has thought of any need to initially boot from a hard disk partition
> which is not the one you want to be your "real" root to reside on.
>
> Well, with multiple hosts on a SCSI bus you do need to do this...
You could boot one of the machines from an IDE disk or from
a floppy or from a network card or you could setup LILO or
whatever loader you are using not to have a default and just
type in the right partition at the command line.
Or you could modify lilo to detect the scsi id or many
possibilities. It sounds a lot simpler than the IP-over-SCSI
stuff itself. There's been some talk about throughput on
IP-over-SCSI: has anyone looked into how fast a SCSI card
will respond in target mode? I seem to remember that there's
some sort of latency problem here.
If people are looking for some new network device, how about
IP-over-SCI? There's an SBus card from Dolphin
(<http://www.dolphinics.no/>) but no PCI card yet so it's a
job for the SPARC-fans. They claim "8 microseconds
Round-Trip Ping-Pong Latency Seen From User Process" for
Solaris 2.4 - that sounds like a good basis for optimising
the Linux IP stack further :-) Throughput is 1 Gbit/s with
10Mb/s "sustained" and max length is 20m. Though $4000 is
rather a lot for a network card. Runs on shielded twisted
pair.
--
Erik Corry erik@arbat.com http://inet.uni-c.dk/~ehcorry/
