[Beowulf] Mutiple IB networks in one cluster
atchley at tds.net
Wed Feb 5 09:33:42 PST 2014
I am not clear as to what you are saying.
I understand non-oversubscribed, fat-tree networks to be described as
non-blocking for "some" bi-sections of the nodes, but not for all
bi-sections. It is possible to block in a "non-blocking" network except on
the local crossbar.
At least that is what Chuck Seitz drove into our heads whenever we said
that a Clos was non-blocking. :-)
On Tue, Feb 4, 2014 at 4:06 PM, Bill Broadley <bill at cse.ucdavis.edu> wrote:
> On 02/01/2014 08:17 AM, atchley tds.net wrote:
> > The cross-bar switch only guarantees non-blocking if the two ports are on
> > the same line card (i.e. using the same crossbar). Once you start
> > traversing multiple crossbars, you are sharing links and can experience
> > congestion.
> Full backplane means no shared links, even if multiple switches are
> Shared links are used when you oversubscribe the uplinks, like with a half
> quarter backplane configuration.
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