[Beowulf] Help with inconsistent network performance
Michael H. Frese
Michael.Frese at NumerEx.com
Tue Dec 18 10:23:17 PST 2007
If you are doing this via nfs, you should be sure that mounts are
done using the tcp parameter in /etc/fstab. Otherwise you may get
udp, and I have seen problems with that as recently as Fedora 8 this morning!
At 08:03 PM 12/17/2007, Brendan Moloney wrote:
>I have a cluster of 8 Linux machines connected with gigabit ethernet
>(full duplex) to a HP Procurve 2848 switch. I am using the
>machines to do interactive distributed rendering. I have noticed
>that the final gather stage (where the intermediate images from the
>render nodes are sent back to the viewing node) has "hiccups" in the
>performance. These hiccups occur with as few as two render nodes,
>and become more common as I add more render nodes. With a 512x512
>image the final gather usually takes a few milliseconds for each
>frame, but when the hiccups occur it is more like 200+ milliseconds.
>Since it is a full duplex switched network, there should not be any
>collisions happening. Since the image is less than 1 MB total, I
>don't think I am saturating the switch. I have checked the contents
>of /sbin/ifconfig and there are zero erroneous packets being
>reported. At this point I am really at a loss as to what is causing
>this. Any input on things to check would be greatly appreciated.
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