[Beowulf] network transfer issue to disk, old versus new hardware
Bogdan.Costescu at iwr.uni-heidelberg.de
Mon Jun 4 08:07:36 EDT 2007
On Sat, 2 Jun 2007, David Mathog wrote:
> I can't quite wrap my head around a recent nettee result, perhaps
> one of the network gurus here can explain it.
IMHO, it's not a network issue, as is shown by your G results.
> sync; accudate; dd if=/dev/zero bs=512 count=1000000 of=test.dat;
All your tests use bs=512 - why ? This makes unnecessary trips to
kernel code and back which result in an increased number of context
switches and significant slowdown. My guess is that this (high number
of context switches) plus a high interrupt rate (disk and network
simultaneously) is the reason for your results.
> Old: Athlon MP 2200+, Tyan S2466MPX mobo, 220.127.116.11 kernel, 512Mb RAM
I used to have the exact same hardware as cluster nodes (but with dual
CPU, whether you also have duals is not clear from your post) and
tried to convert 2 of them to small file-servers - same problem of
disk + network simultaneous activity. After benchmarking, I gave up -
this was almost 2 years ago and I don't have the exact numbers
anymore, but a single PIV 3GHz on a consumer-grade mainboard was able
to provide significantly better performance for the same task.
IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De
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