[Beowulf] building Infiniband 4x cluster questions
john.hearns at mclaren.com
Mon Nov 7 10:45:39 EST 2011
> hi John,
> I had read already about subnet manager but i don't really understand
> this, except when it's only configuration tool.
> I assume it's not something that's critical in terms of bandwidth, it
> doesn't need nonstop bandwidth from the machine & switch is it?
It is critical.
I perhaps am not explaining this correctly.
In an Ethernet network you have a MAC address and the process of ARPing
ie if you want to open a connection to another host on the Ethernet,
you broadcast its IP address and you get returned a MAC address.
Hey, that's why its called an ETHERnet (geddit? Oh, the drollery of
those Xerox engineers)
Anyway, on an Infiniband network the Subnet Manager assigns new hosts a
LID (local identifier)
and keeps track of routing tables between them.
No SM, no new hosts join the network.
An Infiniband expert will be along in a minute and explain that you can
operate a fabric without an SM
and I shall stand corrected.
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