[Beowulf] Infiniband modular switches

Jan Heichler jan.heichler at gmx.net
Fri Jun 13 08:55:10 PDT 2008

Hallo Ramiro,

Freitag, 13. Juni 2008, meintest Du:

RAQ> By the way:

RAQ> a) How many hops a Flextronics 10U 144 Port Modular is doing?


RAQ> b) And the others?

3 too.

RAQ> c) How much latency am I loosing in each hop? (In the case of Voltaire
RAQ> switches: ISR 9024 - 24 Ports: 140 ns ; ISR 2004 - 96 ports: 420 ns

150 ns is the usual value - maybe it is just 140. As far as i know all the switch vendors use the samel 24-port silicon by Mellanox. Because of that you find the same number of switchports everywhere: 24, 144 and 288. 288 is the maximum number of ports you can get when you use a 24port silicon as basis and build a 3-HOP Fat-Tree. 

RAQ> The alternatives are:

RAQ> a) Start with a good 24 port swith and grow up loosing latency and
RAQ> bandwidth

You can use the 24-port switches to create a full bisectional bandwidth network if you want that. Since all the big switches are based on the 24-port silicon this is no problem. 

RAQ> c) Use the Flextronix 10U 144 Port Modular solution which will allow us
RAQ> to scale well in a couple years

But you have to pay now for an expansion that you might never get... Or want a fancy new network technology as soon as you upgrade.

Regards, Jan                            
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