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<p class="MsoNormal">Hello,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">First off, the Lustre that we run here is one that was installed by Intel, so figuring out the exact version seems to be a table lookup on a table internal to Intel, but I’m told it’s probably 2.5-ish…<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Recently, I finally installed a monitoring system on my OSS/MDS servers. And over the last week or so, the OSS servers have been spiking to a 100+ load average (sometimes much higher.) They are not going unresponsive, from what I can
tell, and the processes that are causing it seem to be the ll_ost_io07_XXX processes (where XXX is a number) because they are going into “D” state (io wait state)<o:p></o:p></p>
<p class="MsoNormal"><br>
I recently attended the “The 3rd International Workshop on the Lustre Ecosystem” (GREAT WORKSHOP!!) and via a couple of the talks it got me thinking about tunables.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">One tunable in particular was the ost.threads_max. That guidance on the lustre.org says (1/128MB * num_cpu) which, on my system, works out to well over the max thread count allowable of 512. So my OSS machines are all set to a threads_max
of 512 and indeed on all of the machines, the threads_started is 512. (It’s a VERY busy file system)<br>
<br>
This leads me to the following questions (and possibly more, but let’s start with these):<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="mso-list:Ignore">1)<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Is 512 threads a reasonable setting or should it be lower?<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="mso-list:Ignore">2)<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Is high load “normal” if the file system is under heavy use? At the time I see a lot of open and attr calls which I thought would load the MDS over the OSS… but my under-the-hood understanding is limited at best.<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="mso-list:Ignore">3)<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Should I be looking at other tunables?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I realize the information provided in this initial email is limited as well, so if you are curious about anything else, please let me know what else might be interesting.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Oh and as for the MDS/OSS setup, here’s a brief overview too:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">2x MDS in failover mode with one MDT<o:p></o:p></p>
<p class="MsoNormal">12x OSS in fail over pairs with 12 OST per pair 6 running on each OSS. (72 OST, 6 active on each of 12 OSS for load sharing.)<o:p></o:p></p>
<p class="MsoNormal"> Each OSS pair is hooked to the same set of 2x RAID Array (Dell MD3460)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">--<o:p></o:p></p>
<p class="MsoNormal">Jason Williams<o:p></o:p></p>
<p class="MsoNormal">Assistant Director<o:p></o:p></p>
<p class="MsoNormal">Systems and Data Center Operations.<br>
Maryland Advanced Research Computing Center (MARCC)<br>
Johns Hopkins University<o:p></o:p></p>
<p class="MsoNormal"><a href="mailto:jasonw@jhu.edu">jasonw@jhu.edu</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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