Thank you, I got responses from the following indidivudals
Scooter Morris
William H. Magill
alan_at_nabeth.cxo.dec.com
Larry Clegg
Lavelle Bryan
It appears the feature I was looking for has a name and that name is
"Multipathing" which seems to be the concensus name for what I referred
to as "Load Balancing" two SCSI channels from a host to a storage array.
[Q1] Is multipathing available in 5.0? If so I would upgrade to 5.0 as
I currently run the DU 4.0E flavor of Unix
[Q2] Is it available under DU 4.0E?
A few quotes from the respondents follows. Plus I added a quote which I dug out
a Legato Storage Area Network (SANS) manual because I think sans are the kewl.
Let me start with my quote from the Legato Storage Area Network (SANS) manual.
"Fibre channel is a high-speed, serial interconnect used to attach storage to
servers. It can carry a number of different communication protocols, including
IP and, most importantly, SCSI. At 100MB/sec, it carries five times the
bandwidth of today's common SCSI-2 connections." - Legato
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They go on to imply any server on a SAN could address any SCSI device on that
SAN which I think brings networking to a whole new paradigm. They call this
type of connectivity the "any to any connection environment". Too kewl.
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O.K. here are the quotes from the respondents.
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"The following is definately true for Fibre Channel. Don't know about SCSI.
The [load balancing] feature is officially in the 5.0A release... currently
manufacturing and should start shipping next week."
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"We are running several 5.0 and 5.0a systems, and the feature you are talking
about "multipathing" is definitely supported. We are not currently using it, so
I can't tell you how well it works, or whether it is working with EMC Symmetrix
storage systems specifically, but the OS definitely has the support built in."
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"Tru64 Unix doesn't multipath until 5.0. However, EMC has a product called
Powerpath that does this as well, you should contact them to see if it's
available on your product."
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"An earlier mailing list message was asking about Fibre Channel support. The V5
SPD doesn't say, which implies "No". The V5 release notes suggest that it does,
but the product product manager for V5 told that it wasn't when I asked her.
I was really looking at the relationship of the pieces. Part of what allows
supporting multi-path also helps in supporting Fibre Channel.
[snip snip]
I suspect the set of features is interlocked. To do any load balancing across
I/O adapters (of any sort), you must have a way to identify a device as being
unique no matter what path is used to acces it. Through V4, device addressing
and recognition is based purely on bus address. A device connected through two
busses would have two different names. Without a way to tell them apart, the
kernel would have to present them as separate devices, making host based
failover impossible. So, it seems unlikey that any currently available V4 has
what you need.
In V5 device recognition has been changed to use other information to uniquely
identify devices. However , I don't see the feature reliably mentioned in any
documentation. Since our Fibre Channels controllers are one place such support
could be tested and supported, and V5.0 doesn't have Fibre Channel support, it
seems unlikey that V5.0 has the multi-path feature either.
A feature as major as mult-path support is likey to be mentioned in either the
Software Product Description or the Release Notes for that version."
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So, to summarize it could be supported in V5.0a, maybe, but still not sure.
Thanks for the help.
- Kevin Criss
Received on Wed Apr 19 2000 - 16:13:44 NZST