Myrinet vs. Dolphin

Patrick Geoffray patrick at
Wed Jan 24 11:14:14 EST 2001

Jared Hodge wrote:

> well.  I have several questions though.  First, we are considering
> upgrading our cluster with more nodes, and myrinet seems to have a
> scalability problem in the average cluster size area.  We have 8 nodes


There is no scalability problem in the average cluster size area :-)
It's clear that if you have a 16 ports switch, you will have to get a
new one to connect more than 16 nodes. With two 16 nodes switches, you
can connect up to 30 nodes (one link between the switches) but one link
between 2 switches is a very very poor design (bad bissection). You can
then use more than one link and the mapper with balance the coms between
these inter-switch connections.

The new product (Myrinet 2000 switch M3M) is in production now and will
be added soon on the price list on the web. This new switch is composed
of a rack and slots than contains 8 ports each (8 fibers or 8 Serial or
8 SAN). You can get a huge rack (9U) and buy only one slot with 8 ports
to connect 8 nodes. When you want to upgrade to 32 nodes, you buy 3 more
slots. You can mix link types (one slot fibers and one slot SAN for
Each slot contains a 16 ports full cross-bar and 8 links are connected
to the backplane in the back of the rack in a Clos network (maximum

Ask Myricom sales people for more information.

> I can tell.  Dolphin's switchless technology appears inviting in this

Without switches and with 2 ports per card, you have to do a grid, that
means you share links for coms between differents nodes. It may be
enough for regular applications that talk only to the one-step
Some people believe it's scalable, some people don't. I don't.

Of course, I am biaised in my comments :-)

Hope it gives more information

Patrick Geoffray

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