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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I’d take a look at how the switch ASICs line up with the connections in the system to see if one set is more burdened than another perhaps…<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">And;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">If routing is not handled by the switch, I’d see if there are issues with the way routing is working for the different networks, perhaps there is a different
 path or similar ASIC or other network performance / congestion problem.  Simple network trace route might help flush out some questions; and a conversation with your networking team tracing cables and looking at interface stats.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Charles<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> zhengfeng [mailto:zf5984599@gmail.com]
<br>
<b>Sent:</b> Thursday, March 15, 2012 9:38 AM<br>
<b>To:</b> Hammitt, Charles Allen; lustre-discuss@lists.lustre.org<br>
<b>Subject:</b> Re: RE: [Lustre-discuss] Lustre read performance decay when OSSes are assigned in two different subnet<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-family:"MS PGothic","serif"">Thanks a lot , Charles.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-family:"MS PGothic","serif"">I agree with you about this problem.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-family:"MS PGothic","serif"">And I did more tests with the following steps:<o:p></o:p></span></p>
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<span style="font-family:"MS PGothic","serif"">0) Use</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">3 subnets to</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">assign
 the 3 nodes.<o:p></o:p></span></p>
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<span style="font-family:"MS PGothic","serif"">1<span lang="JA">)</span>Run "netperf" in the</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">two</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">OSS
 separately, run "netserver"</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif""> in "client";this step</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">could
 simulate the</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif""><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-family:"MS PGothic","serif"">networking scenario:</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">"client" reads</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">data
 from two OSS, but here is no disk i/o or</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">other r/w;<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-family:"MS PGothic","serif"">2) two OSS netperf's results</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">are</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">about
 200 M/s, totally are 400M/s. so low - -!<o:p></o:p></span></p>
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<span style="font-family:"MS PGothic","serif"">3) run only netperf at one OSS, the</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">test result is 950M/s.. this res is ok.</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif""><o:p></o:p></span></p>
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<span style="font-family:"MS PGothic","serif"">4)</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">All</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">the
 upper steps prove that, the networking</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">is the bottleneck of the read performance.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif""><o:p></o:p></span></p>
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<span style="font-family:"MS PGothic","serif"">When 2 NODEs send TCP stream at the same time, and only 1 NODE recv TCP stream.</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif"">The total throughput
 is half of normal value. so oddball..<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-family:"MS PGothic","serif"">What induced that?</span><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif""> Thanks a lot<o:p></o:p></span></p>
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<span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif""><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-family:"MS PGothic","serif"">Best regards<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-family:"MS PGothic","serif"">feng<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-family:"Times New Roman","serif""> </span><span style="font-family:"MS PGothic","serif""><o:p></o:p></span></p>
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<b><span style="font-size:9.0pt;font-family:"MS PGothic","serif";color:black">From:</span></b><span style="font-size:9.0pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:9.0pt;font-family:"MS PGothic","serif";color:black"><a href="mailto:chammitt@email.unc.edu">Hammitt,
 Charles Allen</a><o:p></o:p></span></p>
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<b><span style="font-size:9.0pt;font-family:"MS PGothic","serif";color:black">Date:</span></b><span style="font-size:9.0pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:9.0pt;font-family:"MS PGothic","serif";color:black">2012-03-15</span><span style="font-size:9.0pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:9.0pt;font-family:"MS PGothic","serif";color:black">20:50<o:p></o:p></span></p>
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<b><span style="font-size:9.0pt;font-family:"MS PGothic","serif";color:black">To:</span></b><span style="font-size:9.0pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:9.0pt;font-family:"MS PGothic","serif";color:black"><a href="mailto:zf5984599@gmail.com">zf5984599</a>;
<a href="mailto:lustre-discuss@lists.lustre.org">lustre-discuss@lists.lustre.org</a><o:p></o:p></span></p>
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<b><span style="font-size:9.0pt;font-family:"MS PGothic","serif";color:black">Subject:</span></b><span style="font-size:9.0pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:9.0pt;font-family:"MS PGothic","serif";color:black">RE:
 [Lustre-discuss] Lustre read performance decay when OSSes are assigned in two different subnet<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Networking overhead… vlan routing perhaps;  1) with either adding an extra network device hop and latency from a network device/router or 2) overburdened switch
 handling the routing itself still introducing network latency.    Latency is the storage and network i/o bandwidth killer.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I’m willing to bet two things: 
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">1) changing your stripe size from 2 to 1 will make similar bandwidth results to the diagram 2 [54.3MB/s], even if the layout is as diagram 1 [separate nets].<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">2) If all your OSS/MDS and Clients nodes were in the same single vlan network…you’d see better performance than diagram’s 2 54.3MB/sec bandwidth throughput.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">So, drop classful subnets…go with cidr / supernetting networks to get the ip spaces you need and drop the extra routing latency.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Charles<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.0pt;font-family:"Courier New";color:#1F497D">--
<br>
===========================================<br>
Charles Hammitt<br>
Storage Systems Specialist<br>
ITS Research Computing @ <o:p></o:p></span></p>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.0pt;font-family:"Courier New";color:#1F497D">The University of North Carolina-CH<br>
<br>
===========================================<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a href="mailto:lustre-discuss-bounces@lists.lustre.org">lustre-discuss-bounces@lists.lustre.org</a> [<a href="mailto:lustre-discuss-bounces@lists.lustre.org">mailto:lustre-discuss-bounces@lists.lustre.org</a>]
<b>On Behalf Of </b>zhengfeng<br>
<b>Sent:</b> Thursday, March 15, 2012 12:11 AM<br>
<b>To:</b> <a href="mailto:lustre-discuss@lists.lustre.org">lustre-discuss@lists.lustre.org</a><br>
<b>Subject:</b> [Lustre-discuss] Lustre read performance decay when OSSes are assigned in two different subnet<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.5pt;color:black">Dear all,<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;color:black">We met</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">one problem about Lustre read performance decay when OSSes are assigned
 in two different subnet.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;color:black">Describing that in the following diagram:<o:p></o:p></span></p>
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<span style="font-size:10.5pt;color:black">diagram 1, OSS in different subnets:<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:120.0pt">
<span style="font-size:10.5pt;color:black">Client (subnet 10.0.1.2)<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:120.0pt">
<span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"> |<o:p></o:p></span></p>
</div>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:120.0pt">
<span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"> |<o:p></o:p></span></p>
</div>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:120.0pt">
<span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"> |<o:p></o:p></span></p>
</div>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">                </span><span style="font-size:10.5pt;color:black">Switch
<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:96.0pt">
<span style="font-size:10.5pt;color:black">|</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">         </span><span style="font-size:10.5pt;color:black"> |
<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:96.0pt">
<span style="font-size:10.5pt;color:black">|</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">         </span><span style="font-size:10.5pt;color:black"> |<o:p></o:p></span></p>
</div>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:96.0pt">
<span style="font-size:10.5pt;color:black">|</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">         </span><span style="font-size:10.5pt;color:black"> |<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:1.0in"><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">  </span><span style="font-size:10.5pt;color:black"> OSS1</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">      </span><span style="font-size:10.5pt;color:black">
 OSS2<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:1.0in"><span style="font-size:10.5pt;color:black">(10.0.2.2)</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">   </span><span style="font-size:10.5pt;color:black">(10.0.3.2)<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;color:black">For diagram 1, we made the CLient OSS1 and OSS2 in 3 different subnets. the switch</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">used</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">is
 able forward</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">all packages.</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;color:black">Use dd cmd to test r/w performance</span><span lang="ZH-CN" style="font-size:10.5pt;color:black">,</span><span style="font-size:10.5pt;color:black"> write/rad data to/from</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">to</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">OSS1
 and OSS2 at the same time:<o:p></o:p></span></p>
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<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.5pt;color:black">test result:<o:p></o:p></span></p>
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<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<i><span style="font-size:10.5pt;color:black">[root@client</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">client]#</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">time</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">dd</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">if=test2</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">of=/dev/null</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">bs=1M</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">count=2000<o:p></o:p></span></i></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<i><span style="font-size:10.5pt;color:black">2000+0</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">records</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">in<o:p></o:p></span></i></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<i><span style="font-size:10.5pt;color:black">2000+0</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">records</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">out<o:p></o:p></span></i></p>
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<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<i><span style="font-size:10.5pt;color:black">2097152000</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">bytes</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">(2.1</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">GB)</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">copied,</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">53.5922</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">seconds,</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">39.1</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">MB/s<o:p></o:p></span></i></p>
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<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black"><o:p></o:p></span></i></p>
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<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<i><span style="font-size:10.5pt;color:black">real 0m53.796s<o:p></o:p></span></i></p>
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<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<i><span style="font-size:10.5pt;color:black">user 0m0.005s<o:p></o:p></span></i></p>
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<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<i><span style="font-size:10.5pt;color:black">sys 0m2.914s<o:p></o:p></span></i></p>
</div>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"><o:p></o:p></span></p>
</div>
<div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;color:black">diagram 2, OSS in same subnet:<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:120.0pt">
<span style="font-size:10.5pt;color:black">Client (subnet 10.0.1.2)<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:120.0pt">
<span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"> |<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:120.0pt">
<span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"> |<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:120.0pt">
<span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"> |<o:p></o:p></span></p>
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<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">                </span><span style="font-size:10.5pt;color:black">Switch
<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:96.0pt">
<span style="font-size:10.5pt;color:black">|</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">         </span><span style="font-size:10.5pt;color:black"> |
<o:p></o:p></span></p>
<div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:96.0pt">
<span style="font-size:10.5pt;color:black">|</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">         </span><span style="font-size:10.5pt;color:black"> |<o:p></o:p></span></p>
</div>
</div>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:96.0pt">
<span style="font-size:10.5pt;color:black">|</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">         </span><span style="font-size:10.5pt;color:black"> |<o:p></o:p></span></p>
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<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:1.0in"><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">  </span><span style="font-size:10.5pt;color:black"> OSS1</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black">      </span><span style="font-size:10.5pt;color:black">
 OSS2<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:1.0in"><span style="font-size:10.5pt;color:black">(10.0.2.2, 10.0.2.3, at same subnet)<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.5pt;color:black">for diagram 2, we assigned OSS1 and OSS2 at the same subnet, then test:<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.5pt;color:black">test result:<o:p></o:p></span></p>
</div>
<div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;color:black">[root@client219</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">client]#</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">time</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">dd</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">of=/dev/null</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">if=test1</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">bs=1M</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"><o:p></o:p></span></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><i><span style="font-size:10.5pt;color:black">10000+0</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">records</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">in<o:p></o:p></span></i></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><i><span style="font-size:10.5pt;color:black">10000+0</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">records</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">out<o:p></o:p></span></i></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><i><span style="font-size:10.5pt;color:black">10485760000</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">bytes</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">(10</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">GB)</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">copied,</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">193.07</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">seconds,</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">54.3</span></i><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black">MB/s<o:p></o:p></span></i></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black"><o:p></o:p></span></i></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><i><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span></i><i><span style="font-size:10.5pt;color:black"><o:p></o:p></span></i></p>
</div>
</div>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.5pt;color:black">conclusion:<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;color:black">In different subnets, the OSS read performance is 39.1</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">MB/s, while OSS in<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.5pt;color:black">same subnet, the read performance is 54.3</span><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black">MB/s.
 the performance decays so much.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.5pt;color:black">Question:<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt;text-indent:24.0pt">
<span style="font-size:10.5pt;color:black">Why using different subnets in lustre, the performance decayed?<o:p></o:p></span></p>
</div>
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<span style="font-size:10.5pt;color:black">Anyone had met such problems? Many thanks for your answers and advice.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.5pt;font-family:"Times New Roman","serif";color:black"> </span><span style="font-size:10.5pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><b><i><span style="font-size:10.5pt;color:black">B.R.<o:p></o:p></span></i></b></p>
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<p class="MsoNormal" style="margin:0in;margin-bottom:.0001pt"><b><i><span style="font-size:10.5pt;color:black">Feng<o:p></o:p></span></i></b></p>
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