Myrinet vs. Dolphin

[Patrick Geoffray]

Jared Hodge wrote:

> compatible with the older version, they are no longer selling the older
> equipment, so I'm forced to pay for new, bleeding edge technology when
> I'll only be getting the performance of the older technology.  They have

I don't understand (but I don't understand sales in general :-)) ). If
you get the same performance that the old technology at the same price
with the new technology, why do you need to buy the old one ? It's not
an obvious behaviour to sell old products at lower price when a new
product arrives. It's the case for processors because the production
cost is very small (very large volume) and there is a market for old
technology at lower price.

There is a french expression that I like very much : "You want the
butter, the money for selling the butter, and the farmer's wife" :-))

Now, if there is a lot of people that want old tehcnology (cards and
switches), I am sure that Myricom would keep them on sales. But I don't
think the market is big enough to justify to keep two production lines.
Ask Intel for Pentium 75 MHz (what I have in a mail and web server),
they will maybe finish to sell the products they have in their basement
but they won't put back the chip in production.

> forced onto the bleeding edge by our performance demands.  If we had
> known a year ago that we would still have to pay the same amount for the
> same performance now, we probably would have chosen a different option.

Again, I don't understand: how do you want more performance with old
technology ? If you buy Fast Ethernet interfaces and you plug them in a
Gigabit Ethernet switch, you won't have Gigabit links. If you would have
bought old SCI technology and you would buy now new SCI techno (at the
same price again), you would not have better performance with the old
interfaces. It would work (I guess), but half of your cluster would be
slower and the other half faster, and the whole would be slower.

> You would use the 8 SAN ports on each switch for the purpose of
> inter-switch
[...]
>         That makes 3 16-port switches to get to 24 nodes, or $15,000 worth of
> switches, in addition to the $26,000 worth of network cards.  That is a
> scalability problem.

That exactely what I explained in my last email : If you want perfect
bissection, you need to follow David's proposition. If you just want it
to work (and have a very unbalanced cluster), you can just buy another
switch (and why not a new techno, it's the same price) and put only one
link between them.
Now that's the main difference between switch-based interconnect
(Myrinet, Fast and GigEthernet, GigaNet, ServerNet, Quadrics, etc..) and
switch-less interconnect (SCI, Atoll maybe one day). Actually, the
switch-less interfaces have a tiny switch functionnality in the cards,
so when the techno goes up, the routing performance does not follow.

Let me put it clear : I have nothing against Dolphin or SCI specificaly,
it's the switch-less choice that disturb me. The speech "without
switches, we are scalable and we can upgrade very easily" is a little
bit demagogic: it's no more scalable that switch-based interconnect (is
it less ? that's another question) and it does not give you the
possibility to buy old products at lower price.

> and not the very latest Myrinet equipment.  I'm hoping Myricom will
> solve this problem by offering some sort of trade in program or selling
> their surplus older equipment at a lower price.  A trade in program may

There was a such trading possibility to upgrade from Lanai4 cards to
Lanai7 cards in the past (I think it was half price for a new
interface). You need to ask David for such deal for switches.
It seems a very interesting idea to propose a cheap upgrade mechanism
for people that want the top edge and a way to buy used products for
people that does not need the top and would like to buy old products for
less.
I will follow up your proposition to Myricom.

Thanks for your input !

PS: this is my *personnal* point of view and does not mean I talk with
the voice of Myricom. It's a pain to remove the signature to say "it's
me, Patrick" or "it's me, Myricom".

 
Patrick Geoffray

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