In the days when 10MB ethernet was the standard and 40MB/second SCSI-II
was around, it was a good idea, but today with FC-AL, SAA, gigabit
ethernet, etc. there are a lot better options out there for this, which
I stated in the email. There could be some interest in a "poor man's
cluster" with SCSI, but I think I agree that the work effort involved
may offset the bebefits.
:-)
Jeff
Gérard Roudier wrote:
>
> Jeff,
>
> Moving TCP/IP over SPI is probably no longer a great idea.
> Has it ever been so?
>
> We have different media and controllers specifically designed to
> cope with TCP/IP mess-up nowadays. SPI haven't any value to added in
> TCP/IP area, in my opinion.
>
> Your cluster of 3174's was probably a great machine, but time have changed
> and may-be you would use a different solution for an similar problem
> nowadays.
>
> Btw, I donnot mean that having SCSI target mode support would not be
> interesting. This is in my todo list since one year and I haven't find
> time enough for the moment for seriously working on it.
>
> Gérard.
>
> On Fri, 2 Jun 2000, Jeff V. Merkey wrote:
>
> > David,
> >
> > We did something like this on SCSI-II in 1992 while I was at Memorex
> > Telex for our S/370 mainframe cluster controllers. We used high speed
> > SCSI to provide a clustering interconnect for S/370 and 3174 cluster
> > controllers for IBM mainframes. We used an M64 embedded OS, NetWare
> > (gag!) and ATT Unix OS's and I'll share what we discovered.
> >
> > A. You need to write your own SCSI-II initiator and SCSI-II target
> > scripts for the chipsets because there are several special cases you
> > must handle if you are using SCSI as a comm interconnect -- standard
> > disk scripts don't cut it. If you put in these special cases,
> > performance can be stunning and low latency on SCSI.
> >
> > B. We used NCR 53C720 chipsets on the SCSI-II cluster adapters we
> > designed for the 1174 and 9432 (3172/3088) cluster controllers. We
> > discovered that SCSI and S/370 channel had a lot of similiar behaviors
> > in terms of data transfer architectures, and after 8 months of profiling
> > and analysis, discovered that the 3088 method used by IBM was ideal when
> > applied to a SCSI-II interconnect.
> >
> > C. The best method is to reserve two SCSI addresses per system, one for
> > reads and one for writes. The IBM 3088 cluster controller does
> > something similiar, it reserves a range of subchannel addresses (very
> > similar to SCSI LUN addressing) and reserves some for writes and some
> > for reads. On IBM channel, there is the ability to present two statuses
> > which will tell the host controller when the I/O is completed
> > (Channel-End) and when the channel device is ready to receive the next
> > request (Device-End). On the read side, a 3088 will hold off
> > Device_ending status to "prime" the device for the next read. You kind
> > of need to do this since S/370 channel and SCSI both have this concept
> > of master-slave and writes are "pushed" and reads "pulled" from the
> > target by using selection and reselection protocols. We did something
> > very similar to handle special case for multiple outstanding asynch
> > reads from a SCSI-II address. We mapped IP addresses and adapter
> > addresses to each R/W pair of SCSI addresses.
> >
> > D. With this, we were able to route TCP/IP, IPX/SPX, LLC8022, and all
> > these different LAN protocols at very high data rates, and across
> > multiple pairs of SCSI-II LUN addresses and SCSI-II adapters in a
> > cluster, as well as standard SNA Request Unit traffic, to Network
> > servers and devices as well as S/370 mainframes, 3172 gateways, etc.
> > and at very low latency.
> >
> > Whether someone has done this on Linux I don't know, but someone like
> > Gerard Roudier could easily whip out some SCSI scripts to do this, and
> > envelope it with the Network routers in Linux. Network interconnects
> > are a lot faster these days, and there's SSA, and Fibre Channel, and all
> > this other stuff that is much better designed than SCSI. If you are
> > interested in doing something with SCSI, here's some ideas to consider.
> >
> > :-)
> >
> > Jeff
> >
> > Rogier Wolff wrote:
> > >
> > > david wrote:
> > > > has any one got tcp/ip over scsi working ?
> > > > if not i am going to try it my self
> > > > as i need the bandwidth
> > >
> > > > also if any one has any info to help this project please let me know
> > > > as the more help the better
> > >
> > > The consensus on Linux-kernel is that you should buy a few gigabit
> > > ethernet cards.
> > >
> > > Roger.
> > >
> > > --
> > > ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 **
> > > *-- BitWizard writes Linux device drivers for any device you may have! --*
> > > * Common sense is the collection of *
> > > ****** prejudices acquired by age eighteen. -- Albert Einstein ********
>
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