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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">Hi,
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">I think that
</span><span style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US"><a href="https://wiki.mikejung.biz/KVM_/_Xen"><span lang="EN-US">https://wiki.mikejung.biz/KVM_/_Xen</span></a></span><span style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">
<span lang="EN-US">might be quite useful<o:p></o:p></span></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">Pretty much there won’t be a universal recipe but rather combination of what are kernel/QEMU/OpenStack… versions<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">and implementation choices that were made<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">-Guest OS/host OS kernel version<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">-QEMU version<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">-OpenStack release. Basically the part of XML definition of disk is controlled by OpenStack
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">-virtio_blk vs. some fully-virtualized stuff like ide is used
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">-the backend for virtual disk
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">some points possibly to add to that article:<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US"><span style="mso-list:Ignore">1)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">For virtio_scsi in OpenStack see
<a href="https://blueprints.launchpad.net/nova/+spec/cinder-backend-report-discard">
https://blueprints.launchpad.net/nova/+spec/cinder-backend-report-discard</a> <o:p>
</o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US"><span style="mso-list:Ignore">2)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">Linux itself is supposed to detect if it works on HDD or SSD<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">See:<o:p></o:p></span></p>
<p class="MsoListParagraph"><code><span lang="EN-US" style="font-size:9.0pt;color:#555555">smartctl -a /dev/sd<x><o:p></o:p></span></code></p>
<p class="MsoListParagraph"><code><span lang="EN-US" style="font-size:9.0pt;color:#555555">and</span></code><span lang="EN-US" style="font-size:9.0pt;font-family:Consolas;color:#555555;background:#F4F4F4"><o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">cat /sys/block/sd<x>/queue/rotational<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">(0 –SSD, 1 – HDD)<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">But results might be contradictory/interpretation of that is not straightforward.<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">Maybe someone has better insight, but what I understood from one hand not all SSD drives report to being as
such <o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">And that’s why sysfs entry /sys/block/sd<x>/queue/rotational was introduced which was meant to enforce ‘SSD-like
behavior)<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US"><a href="https://lwn.net/Articles/408428/">https://lwn.net/Articles/408428/</a>
<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">But then I kinda understood that Linux might/is supposed to set it correctly (via udev rules?)
<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">But it should be noted in Ubuntu 12.04/Ubuntu 14.04 that I worked with that had SSDs this flag /rotational
was ‘1’ on SSD, ie. Incorrect…)<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span lang="EN-US" style="color:#242729"><span style="mso-list:Ignore">3)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">The question of cfq vs. deadline vs. noop scheduler (apparently both in guest and host) where decision
should be based on workloads/recommendations of OS vendor (/which again might be release-dependent).</span><span lang="EN-US" style="color:#242729;background:#EFF0F1"><o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="color:#242729;background:#EFF0F1"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">BR.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US">Konstantin<o:p></o:p></span></p>
<p class="MsoListParagraph"><span lang="EN-US" style="color:#242729;background:#EFF0F1"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:"Trebuchet MS",sans-serif;color:#44546A;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt">From:</span></b><span lang="EN-US" style="font-size:11.0pt"> Tim Bell [mailto:Tim.Bell@cern.ch]
<br>
<b>Sent:</b> Friday, August 05, 2016 12:44 PM<br>
<b>To:</b> openstack-operators <openstack-operators@lists.openstack.org><br>
<b>Subject:</b> [Openstack-operators] Tuning I/O with SSDs<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Has anyone a good recipe for improving I/O performance when the hypervisor has SSDs ?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">The configuration is CentOS 7 for guest and hypervisor with KVM.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Tim<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
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