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<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi, joe<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks for your replay.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">I want to confirm whether we use “--rescan” for another reason.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">If only for connecting volume, it should be a bug. I will report it soon.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Joe Gordon [mailto:joe.gordon0@gmail.com]
<br>
<b>Sent:</b> Wednesday, August 27, 2014 1:12 AM<br>
<b>To:</b> OpenStack Development Mailing List (not for usage questions)<br>
<b>Subject:</b> Re: [openstack-dev] [OpenStack][Nova]May be performance issues of connect_volume in Nova<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">On Tue, Aug 26, 2014 at 5:36 AM, Wang Shen <<a href="mailto:ws1210@gmail.com" target="_blank">ws1210@gmail.com</a>> wrote:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Hi, All<br>
I have done some work to test the performance of LUN scanning, use<br>
"iscsiadm" with "--rescan" like what Nova dose. In my test, a host<br>
connected with a lot of LUNs , more than 1000 LUNs. Because "--rescan"<br>
will cause kernel to scan all of the LUNs connected to the host, it<br>
costs several minutes to complete the scanning.<br>
<br>
According to "connect_volume" at line 284 in <a href="http://nova.virt.libvirt.volume.py" target="_blank">
nova.virt.libvirt.volume.py</a>:<br>
<a href="https://github.com/openstack/nova/blob/master/nova/virt/libvirt/volume.py#L252" target="_blank">https://github.com/openstack/nova/blob/master/nova/virt/libvirt/volume.py#L252</a><br>
Nova uses "iscsiadm" with "--rescan" to detect new volume, but this<br>
command will scan all of the LUNs, including all the others which<br>
already connected to this host. So if a host has a large number of<br>
LUNs connected to it, the connect_volume will be very slow.<br>
<br>
I think connect_volume needn't scan all of the LUNs, only need scan<br>
the LUN specified by connection_info.<br>
<br>
Is it necessary to discuss a more efficient way to improve this issues.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">It sounds like this is a bug; we use <a href="https://bugs.launchpad.net/nova">
https://bugs.launchpad.net/nova</a> to track bugs so they don't get lost.<o:p></o:p></span></p>
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--<br>
Best wishes<br>
====================== Peter.W ======================<br>
<br>
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<a href="http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev" target="_blank">http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev</a></span><span lang="EN-US"><o:p></o:p></span></p>
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