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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I guess the question I’m really asking here is: “Since we know resize down won’t work in all cases, and the failure if it does occur will be hard for the user
to detect, should we just block it at the API layer and be consistent across all Hypervisors ?”<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext"> Andrew Laski [mailto:andrew.laski@rackspace.com]
<br>
<b>Sent:</b> 13 June 2014 13:57<br>
<b>To:</b> OpenStack Development Mailing List (not for usage questions)<br>
<b>Subject:</b> Re: [openstack-dev] [nova] Do any hyperviors allow disk reduction as part of resize ?<o:p></o:p></span></p>
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<p class="MsoNormal">On 06/13/2014 08:03 AM, Day, Phil wrote:<o:p></o:p></p>
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<p class="MsoNormal">>Theoretically impossible to reduce disk unless you have some really nasty guest additions.<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">That’s what I thought – but many of the drivers seem to at least partially support it based on the code, hence the question on here to find out of that is really
supported and works – or is just inconsistent error checking across drivers.</span><o:p></o:p></p>
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My grumpy dev answer is that what works is not resizing down. I'm familiar with the xen driver resize operation and will say that it does work when the guest filesystem and partition sizes are accommodating, but there's no good way to know whether or not it
will succeed without actually trying it. So when it fails it's after someone was waiting on a resize that seemed like it was working and then suddenly didn't.<br>
<br>
If we want to aim for what's going to work consistently across drivers, it's probably going to end up being not resizing disks down.<br>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> Aryeh Friedman [<a href="mailto:aryeh.friedman@gmail.com">mailto:aryeh.friedman@gmail.com</a>]
<br>
<b>Sent:</b> 13 June 2014 11:12<br>
<b>To:</b> OpenStack Development Mailing List (not for usage questions)<br>
<b>Subject:</b> Re: [openstack-dev] [nova] Do any hyperviors allow disk reduction as part of resize ?</span><o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">Theoretically impossible to reduce disk unless you have some really nasty guest additions.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"> <o:p></o:p></p>
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<p class="MsoNormal">On Fri, Jun 13, 2014 at 6:02 AM, Day, Phil <<a href="mailto:philip.day@hp.com" target="_blank">philip.day@hp.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hi Folks,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I was looking at the resize code in libvirt, and it has checks which raise an exception if the target root or ephemeral disks are smaller than the current ones – which seems fair
enough I guess (you can’t drop arbitary disk content on resize), except that the because the check is in the virt driver the effect is to just ignore the request (the instance remains active rather than going to resize-verify).<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">It made me wonder if there were any hypervisors that actually allow this, and if not wouldn’t it be better to move the check to the API layer so that the request can be failed rather
than silently ignored ? <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">As far as I can see:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">baremetal: Doesn’t support resize<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">hyperv: Checks only for root disk (<a href="https://github.com/openstack/nova/blob/master/nova/virt/hyperv/migrationops.py#L99-L108" target="_blank">https://github.com/openstack/nova/blob/master/nova/virt/hyperv/migrationops.py#L99-L108</a>
)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">libvirt: fails for a reduction of either root or ephemeral (<a href="https://github.com/openstack/nova/blob/master/nova/virt/libvirt/driver.py#L4918-L4923" target="_blank">https://github.com/openstack/nova/blob/master/nova/virt/libvirt/driver.py#L4918-L4923</a>
)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">vmware: doesn’t seem to check at all ?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">xen: Allows resize down for root but not for ephemeral (<a href="https://github.com/openstack/nova/blob/master/nova/virt/xenapi/vmops.py#L1015-L1032" target="_blank">https://github.com/openstack/nova/blob/master/nova/virt/xenapi/vmops.py#L1015-L1032</a>
)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">It feels kind of clumsy to have such a wide variation of behavior across the drivers, and to have the check performed only in the driver ?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#888888"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#888888">Phil</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#888888"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
_______________________________________________<br>
OpenStack-dev mailing list<br>
<a href="mailto:OpenStack-dev@lists.openstack.org">OpenStack-dev@lists.openstack.org</a><br>
<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><o:p></o:p></p>
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<p class="MsoNormal"><br>
<br clear="all">
<br>
-- <o:p></o:p></p>
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<p class="MsoNormal">Aryeh M. Friedman, Lead Developer, <a href="http://www.PetiteCloud.org" target="_blank">
http://www.PetiteCloud.org</a><o:p></o:p></p>
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<br>
<o:p></o:p></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>OpenStack-dev mailing list<o:p></o:p></pre>
<pre><a href="mailto:OpenStack-dev@lists.openstack.org">OpenStack-dev@lists.openstack.org</a><o:p></o:p></pre>
<pre><a href="http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev">http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev</a><o:p></o:p></pre>
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