Re: White paper: CHARON-VAX cluster w/ shared SCSI disks

From: David Froble (davef_at_tsoft-inc.com)
Date: 10/14/03 

Date: Mon, 13 Oct 2003 21:43:42 -0400

Michael Moroney wrote:

> "Rob Lyons" <rob.lyons@resilientsys.com> writes:
>
>
>>Thanks for getting the word out to the rest of us who were not able to attend the Dutch Technical Update Days.
>>
>
>>I suggest the name for your configuration is LAVC with shared SCSI or a Mixed Interconnect Cluster since the interconnect that
>>carries the cluster traffic names the cluster type, by convention. The term "SCSI-cluster" incorrectly implies that the SCSI bus is
>>carrying SCA cluster traffic.
>>
>
> Well, no, to be picky the term LAVC was obsolete with VMS V5. In the old
> days (VMS V4.x) 'big vax' clusters (CI) were different beasts from
> microvax clusters (LAVC) running MicroVMS. Nowadays 'a cluster is a
> cluster is a cluster'.

Ok, being picky, I'll disagree. A cluster has always been a cluster, regardless
of the interconnect used for moving data and for DLM traffic. The only real
difference that I'm aware of with the LAVC was the name. Use of Ethernet to
build a cluster was not limited to the MV systems. It's a bit like looking for
a difference between VMS and OpenVMS.

What the CI did was allow direct access to storage by each system. Systems
without such an interconnect were forced to serve all disks from the system they
were/are connected.

> re base note: Since Charon-VAX emulates a VAX not Alpha and shared
> SCSI was never on VAX, the VAX SCSI drivers may assume they're the
> only thing accessing the bus and there may some 'strangeness' seen.
> But interesting nonetheless.
>

I'm with you on wondering about 2 masters on the SCSI bus. I don't know much
about differential SCSI, well, SCSI in general, and therefore don't know if the
differential SCSI hardware handles such.

I haven't worked with any of the emulators yet. With VMS systems sitting on the
shelf because this one person can barely justify running 3 VMS systems, the need
for alternate hardware has not yet occured. But, as new x86 based systems and
capabilities become available, thoughts of using some of the new capabilities
with VAX emulators is as you say, interesting.

Dave 

-- 
David Froble                       Tel: 724-529-0450
Dave Froble Enterprises, Inc.      Fax: 724-529-0596
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Vanderbilt, PA  15486

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