[Beowulf] Infiniband modular switches

Jan Heichler jan.heichler at gmx.net
Fri Jun 13 10:43:31 PDT 2008

Hallo Ramiro,

Freitag, 13. Juni 2008, meintest Du:

RAQ> On Fri, 2008-06-13 at 17:55 +0200, Jan Heichler wrote:

>> 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> Yes, But How many ports must I waste if I do not want to loose to much
RAQ> bandwidth.

Exactly 50%. 12 Ports go to clients and 12 ports go to the spine. I can send you a sketch if you are interested. 

RAQ> And about latency, It could be negligible compared to latency at the
RAQ> infiniband card (~3 microsecs in front of 480 nanosecs at switch),
RAQ> right?

The number of HOPs is always the same... 3 up to 288 ports. With the new 36 port silicon that will change. Up to 648 Clients with 3 HOPs if i'm not wrong. 

>> 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.

RAQ> Well, I most probably will be needing 48 ports in five months and 120
RAQ> ports in about a year

48 Ports is 6 24 Port Switches. 

here is a quick overview:

client ports		#of 24 port switches you need for full bisectional bandwidth
24			1
36			5
48			6
60			8
72			9
84			11
96			12
108			14
120			15
132			16
144			18

Somewhere around 11 and 14 is normally the break even for a 144-port switch - depends on your cost prices of course ;-)

I hope i didn't miscalculate ;-)

RAQ> Thanks for your answer

Any time!

Regards, Jan                            
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