Hi All Beowulfers, Continuing reports Joshua was nice to share, I want to report some pilot testing of the switch I got -- I went for a cheap (~700$ for 44 ports) D-Link DGS-1248T. Did firmware upgrade on it as soon as it arrived (had to use laptop with windows since firmware upgrade is available only in the tool which shipped along -- web interface of the switch doesn't allow it)
I banged by hand against the way for a few minutes since I could not find any nice tool to perform parametric analysis/plotting of network performance (please advice if there is any), thus I wrote two small scripts - one to collect and another to plot the results. By default it uses netperf and plots throughput between two nodes depending on MTU sizes. Scripts are available from http://www.onerussian.com/Linux/scripts/netperf/test_netperf.sh http://www.onerussian.com/Linux/scripts/netperf/plot_test.py Graphs are available from http://www.onerussian.com/Linux/scripts/netperf/examples/ Tuned parameters were (blindly copied from Joshua :-)) net.ipv4.tcp_wmem = 4096 65536 16777216 net.ipv4.tcp_rmem = 4096 16777216 16777216 net.core.rmem_max = 8388608 net.core.wmem_max = 8388608 whenever defaults are net.ipv4.tcp_wmem = 4096 16384 131072 net.ipv4.tcp_rmem = 4096 87380 174760 net.core.wmem_max = 131071 net.core.rmem_max = 131071 Results: weirdo -- needs to rerun may be -- there is a range of MTUs (0 - ~4500) when switch performed better than crossover with the same network parameters MTUs 3500-4000 seems to be the best in terms of throughput (~185000 KBps duplex) and tuning the params seems to help in general but for 3500 seems to be not that important (need to run with smaller step of MTU) going away from default MTU (1024) helps a lot for CPU utilization, so my NFS server should be happier than now. but "tuned" params incure their own impact on cpu utilization, thus they also has to be checked for their optimal values for the task generally this DLink seems to be not as good as Joshua's SMC on high MTU sizes -- speed between crosslinked and via-switch diverges considerably (around 30000-35000 KBps loss) I hope this is of help for anyone ;) -- .-. =------------------------------ /v\ ----------------------------= Keep in touch // \\ (yoh@|www.)onerussian.com Yaroslav Halchenko /( )\ ICQ#: 60653192 Linux User ^^-^^ [175555]
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