SintMaarten network
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Revision as of 13:25, 24 November 2009 by Janjust@nikhef.nl (talk | contribs)
In October 2009 the SintMaarten cluster was commissioned. This cluster is based on HP blades. Soon after commissioning a serious performance issue was reported:
[BG-NLT1-Support] #287: bad gridftp transfer rate - smrt wns
This page is the result of the analysis of this performance issue.
Problem report
The performance issue reported was seen when copying a file from the Nikhef storage system to a SintMaarten worker node. Transfer speeds at first were OK but dropped to very low levels after about 120 Mb of data, eventually causing timeouts in the lcg-cp command used. Copying the exact same file from the exact same storage element to a slightly older worker node did not experience this problem:
===
wn-smrt-006 (Bad!)
===
# lcg-cp --vo atlas -v srm://.... file://.....
[snip]
# streams: 1
62914560 bytes 1279.98 KB/sec avg 512.00 KB/sec inst
vs
===
wn-val-066 (Good!)
===
# lcg-cp --vo atlas -v srm://.... file://.....
[snip]
# streams: 1
1672478720 bytes 68053.21 KB/sec avg 70142.84 KB/sec inst
Analysis
This At first it was thought that the lcg-cp command itself was causing the error
