Keith Parris wrote:
> Richard Maher wrote:
>> 1) I saw 10 Gigabit NIC sup****t 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 s__t-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?
>
> 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.
>
>> I mean, if I was an Rdb engineer that had used p___-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. . .
>
> Rdb sup****ts Row Cache in Galaxy Shared Memory between multiple nodes.
>
>> 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?
>
> 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 sup****t, 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.
>
>> 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?
>
> 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. ---
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.
> 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.
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