Hi,

I was flicking through the OpenVMS Roadmap presentation yesterday and came
across a couple of very interesting (at least to me) milestones regarding
Cluster Interconnects. Now, I'm pretty useless with hardware, "the laws of
physics capt'n", and not much better as a System Manager so I hope someone
can offer me a lay-man's view of what these developments could mean for VMS
Cluster performance. (In particular the VMS Lock Manager.)

1) I saw 10 Gigabit NIC support scheduled for VMS 8.3 (Depending on which
slide you look at it says "Integrity Servers Only"). Now 10x what a lot of
people are using for a cluster-interconnect at the moment sounds pretty
shit-hot to me! Especially if you're moving big lock-trees around the
cluster. Given that this functionality is less than a year away, surely some
performance figures or at least anecdotal evidence should be available? I
mean, if I was an Rdb engineer that had used piss-poor DLM performance as
the rationale for sticking all of my R&D eggs in the stand-alone single-node
basket, then I'd be interested in what's happening with this. Right? "But
it's not the bandwidth, it's the latency that gets ya." Well that brings me
to the next slide. . .

2) Next Generation Low-Latency Interconnects Post 8.3 (Integrity Servers
Only)

Am I the only person getting their jollies out of this or what?

I forget when Oracle10g was scheduled to arrive but I'd dearly love to hear
from anyone using Cache Fusion and is looking at this!

Will there be a special limit on the distances between nodes for this stuff
to work? (Like memory channel) Can you have a Disaster Tolerant Low Latency
Cluster?

Regards Richard (Just off to have a cold shower) Maher

Low latency is where the performance appears to be, gig ethernet, and maybe
10g ethernet have too much latency as you scale
"Richard Maher" <maher_rj (AT) hotspamnotmail (DOT) com> wrote

Richard Maher wrote:
..
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I'd be a lot more excited if they weren't artifically limiting it to the
intel based servers. It'll be a long time before those capabilities 'on
integrity' matter to us or any of our customers.

Still, its good news for the long run.

"Bill" <bill (AT) demsky (DOT) name> writes:

Almost everyone I've talked to did not know that GBE over copper
runs 4 120Mbaud lines and has to do a line turnaround, unlike
fibre where it is a real full duplex circuit. With a lot of
small packets, throughput tanks and latency blows out.

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.

Richard Maher wrote:
One way to estimate the impact is to see how Gigabit Ethernet compared
with Fast Ethernet. Bandwidth went up by close to 10x; latency went from
about 240 microseconds for a round-trip lock conversion request with
Fast Ethernet to about 200 microseconds on Gigabit Ethernet, as measured
on a typical Alpha box of the recent past (Wildfire or ES40). So don't
expect a 10x latency improvement.

Rdb supports Row Cache in Galaxy Shared Memory between multiple nodes.

Nope. I also find this exciting.

Potential candidate technologies one would naturally want to look at
could include Infiniband and RDMA/iWARP.

Infiniband promises low latency, but hasn't really taken off much in the
industry yet, and hardware is expensive. Some initial proponents have
subsequently backed out (like Intel). A lot of people are waiting to see
how this turns out.

RDMA/iWARP looks to have broad potential industry support, and will
quite possibly be built into commodity Ethernet adapters. Latency
wouldn't be quite as low, but price would be low and price/performance
very good.

Should be interesting. In any case, I'm know VMS Engineering has its
finger on the pulse of the technologies available in the marketplace,
and will provide a quality solution with the best interests of the
customers in mind.

Infiniband has some fairly low distance limitations, unless you include
an Infiniband router, and that's for IP traffic.

For anything Ethernet-based I don't expect distance limitations. Other
than how far you can drive light over fiber, there's no inherent
distance limit in Gigabit Ethernet today, for example. But of course the
longer your inter-site distance, the more delay there is due to the
speed of light over the distance, which mitigates against low latency.
---
Looks likely I'll be doing a hands-on workshop at HP Technology Forum on
Long-Distance OpenVMS Clusters. We'll explore some of the impacts of
long distances on performance in that workshop, for folks who are
interested.

Keith Parris wrote:
Indeed - it is the physical absolute barrier for comminucation of data or
energy over distance, something to do with instantaneous causal events not
being possible and all that (if I recall my physics of relativity correctly)
:-)

Dweeb.

Dr. Dweeb wrote:
But perhaps not http://homepage.sunrise.ch/homepage/...pace-time.html

Dweeb.