Description of problem:<br />
<br />
NFS Client READ performance drops significantly after a while , maybe after the filling up of the memory with cache data. For a large enough binary file on the nfs server read on the client with <br />
dd if=bigfile of=/dev/null bs=1M<br />
the read performance will significantly drop after some time (the file needs to be large enough ).<br />
This performance degradation does NOT happen if dd is used with iflag=direct<br />
Also, it seems that older (EL5 generation) kernels do not suffer from this issue.<br />
<br />
<br />
Version-Release number of selected component (if applicable):<br />
<br />
Tests were made with :<br />
Servers :<br />
2.6.32-358.2.1.el6.x86_64 and another machine with<br />
2.6.32-279.22.1.el6.x86_64 <br />
Storage IS fast enough.<br />
<br />
Clients :<br />
2.6.32-358.6.2.el6.x86_64,24G RAM - this one drops in performance (unless the sequential read is done in direct mode).<br />
2.6.18-348.6.1.el5 also 24G RAM - this one works fine.<br />
<br />
Network used was gigabit; Issue is not caused by the network, iperf is able to fill the bandwidth for an indefinite ammount of time.
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