[Beowulf] NFS Read Errors

Michael H. Frese Michael.Frese at NumerEx.com
Fri Dec 7 12:28:14 EST 2007


Skylar,

An interesting suggestion.  I'll look into it.  Thanks.


Mke


At 09:57 AM 12/7/2007, Skylar Thompson wrote:
>Michael H. Frese wrote:
> > Fourth, with ttcp over tcp, I found that the troubled machine could
> > send 800 MB in about 20 seconds -- the wire speed for those 32-bit PCI
> > slots as tested by netpipe.  However, if I used ttcp over udp, I
> > couldn't reliably send even ten 8192-byte blocks!  Successive sends
> > and receives would receive 3, or 1, or 5 blocks.  Don't ask me how
> > these two facts are compatible.  I don't know.
>
>This sounds like it could be a flow control issue. TCP does its own flow
>control, but UDP doesn't. Some Ethernet switches do IEEE 802.3x, which
>might help your UDP performance.
>
>--
>-- Skylar Thompson (skylar at cs.earlham.edu)
>-- http://www.cs.earlham.edu/~skylar/
>
>
>

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