[Beowulf] Mutiple IB networks in one cluster

[Greg Lindahl]

I'm saying that's what the definition of a Clos network is,
and that's the only situation in which it's "non-blocking".

People buy clusters with all kinds of network configurations.

On Thu, Feb 06, 2014 at 09:51:10PM -0600, Alan Louis Scheinine wrote:
> When I wrote "the number of nonblocking connections is typically
> much less than the number of nodes" I had in mind the telephone
> network (in the age of copper wires).  Are you sure that "1/2 the
> nodes can make a single call to the other 1/2 of the nodes" is
> typical of a computer interconnect?  I thought that the typical
> cross-sectional bandwidth was less, or am I mistaken?
> Alan Scheinine
>
> Greg Lindahl wrote:
>> In the usual Clos network, 1/2 of the nodes can make a single call to
>> the other 1/2 of the nodes. That's what's non-blocking. Nothing else
>> is. Running any real code, every node talks to more than one other
>> node, and the network is not non-blocking.
>>
>> It makes perfect sense in a telephone network. In the real world, a
>> Clos network is good but not non-blocking.
>>
>> On Wed, Feb 05, 2014 at 06:31:11PM -0600, Alan Louis Scheinine wrote:
>>> Clos is non-blocking up to a certain number of completed connections.
>>> The number of nonblocking connections is typically much less than
>>> the number of nodes for which the Clos network provides service.
>>> Anybody can make a telephone call to anybody else, up until the
>>> maximum number of completed connections is reached.
>>>> At least that is what Chuck Seitz drove into our heads whenever we said that a Clos was non-blocking. :-)
>>>>
>>>> Scott
>>>>
>>> -- 
>>>
>>>  Alan Scheinine
>>>  200 Georgann Dr., Apt. E6
>>>  Vicksburg, MS  39180
>>>
>>>  Email: alscheinine at tuffmail.us
>>>  Mobile phone: 225 288 4176
>>>
>>>  http://www.flickr.com/photos/ascheinine
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>
> -- 
>
>  Alan Scheinine
>  200 Georgann Dr., Apt. E6
>  Vicksburg, MS  39180
>
>  Email: alscheinine at tuffmail.us
>  Mobile phone: 225 288 4176
>
>  http://www.flickr.com/photos/ascheinine