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--></style></head><body lang="EN-US" link="blue" vlink="purple" style="word-wrap: break-word;-webkit-nbsp-mode: space;-webkit-line-break: after-white-space"><div class="WordSection1"><p class="MsoNormal"><span style="color:#1F497D">Hi Paul,</span></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span></p><p class="MsoNormal"><span style="color:#1F497D">I agree that changing image/flavor is not truly required, but like I said below it is not the primary intended use case. The usecase is we want to move an instance with same volume/ip/identity to move to another host when the original host has failed.</span></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span></p><p class="MsoNormal"><span style="color:#1F497D">--Shyam</span></p><p class="MsoNormal"><span style="color:#1F497D"> </span></p><div><div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><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""> Paul Voccio [mailto:<a href="mailto:paul.voccio@rackspace.com">paul.voccio@rackspace.com</a>] <br>
<b>Sent:</b> Tuesday, November 29, 2011 11:58 AM<br><b>To:</b> Shyam Kaushik; <a href="mailto:openstack@lists.launchpad.net">openstack@lists.launchpad.net</a><br><b>Subject:</b> Re: [Openstack] Rebuild instance from failed host</span></p>
</div></div><p class="MsoNormal"> </p><div><p class="MsoNormal"><span style="font-size:10.5pt;color:black">Hi Shyam,</span></p></div><div><p class="MsoNormal"><span style="font-size:10.5pt;color:black"> </span></p></div><div>
<p class="MsoNormal"><span style="font-size:10.5pt;color:black">The initial use case sounds reasonable but I'm not sure I see the need to change flavor and image ref. That is essentially a new instance with the same ip and volume? Is there a real need there then? I might think that adding some logic around a rebuild that has a failed host that would know to rebuild on another host would keep in line with 'rebuild' logic. If it changed all of the data about the instance it doesn’t feel much like a 'rebuild' anymore. </span></p>
</div><div><p class="MsoNormal"><span style="font-size:10.5pt;color:black"> </span></p></div><div><p class="MsoNormal"><span style="font-size:10.5pt;color:black">Just my thoughts. </span></p></div><div><p class="MsoNormal">
<span style="font-size:10.5pt;color:black">pvo</span></p></div><div><p class="MsoNormal"><span style="font-size:10.5pt;color:black"> </span></p></div><div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="color:black">From: </span></b><span style="color:black">Shyam Kaushik <<a href="mailto:shyam@zadarastorage.com">shyam@zadarastorage.com</a>><br><b>Date: </b>Tue, 29 Nov 2011 11:34:08 +0530<br>
<b>To: </b><<a href="mailto:openstack@lists.launchpad.net">openstack@lists.launchpad.net</a>><br><b>Subject: </b>[Openstack] Rebuild instance from failed host</span></p></div><div><p class="MsoNormal"><span style="font-size:10.5pt;color:black"> </span></p>
</div><blockquote style="border:none;border-left:solid #B5C4DF 4.5pt;padding:0in 0in 0in 4.0pt;margin-left:3.75pt;margin-right:0in" id="MAC_OUTLOOK_ATTRIBUTION_BLOCKQUOTE"><div><div><p class="MsoNormal"><span style="color:black">Hi Folks,</span></p>
<p class="MsoNormal"><span style="color:black"> </span></p><p class="MsoNormal"><span style="color:black">Today in openstack, “rebuild” instance tears down a running instance & sets up a fresh instance in its place on the same host. “resize” instance migrates the underlying instance disk to another physical host and spawns the instance there. However both these options require that the origin host that was running the instance to be up for the operations to work. If the host is failed (could be irrecoverable if the root FS is corrupted), we cannot recover the instance. All operations on that instance would fail.</span></p>
<p class="MsoNormal"><span style="color:black"> </span></p><p class="MsoNormal"><span style="color:black">We want to introduce a new “rebuild instance from failed host” operation whereby we could rebuild the instance on another host with the same properties (instance-id, name, network info, metadata, volume attachments) and mark the old instance on failed host for cleanup. Whenever the failed host comes up, it will clear cache for the old instance. This operation is essentially a modified form of today’s “rebuild” instance, in terms of allowing to rebuild the instance even if the underlying host has failed. </span></p>
<p class="MsoNormal"><span style="color:black"> </span></p><p class="MsoNormal"><span style="color:black">Essentially the “rebuild instance from failed host” will do the following steps:<br># See if it can terminate running instance on existing host. If not create a migration record</span></p>
<p class="MsoNormal"><span style="color:black"># Change “host” for instance to a new host (picked up by scheduler) & spawn the instance on that host (with volume attachments, networks connected as it was with the original instance)</span></p>
<p class="MsoNormal"><span style="color:black"># Optionally during this procedure allow instance flavor to be changed + possibility to give a different “image reference” for it to bootup (could possibly be used to upgrade OS image of the instance during this procedure).</span></p>
<p class="MsoNormal"><span style="color:black"># Whenever the failed host comes up, it will read through migration records (as part of init_host), clear up its cache & mark the migration complete.</span></p><p class="MsoNormal">
<span style="color:black"> </span></p><p class="MsoNormal"><span style="color:black">Note that this procedure could also be used for Upgrading image versions + changing instance flavors even when the origin host is alive, but that is not the primary intended use case.</span></p>
<p class="MsoNormal"><span style="color:black"> </span></p><p class="MsoNormal"><span style="color:black">Question is, is this a reasonable proposal to go forward? If not, are there any other alternative procedures available to meet the requirement?</span></p>
<p class="MsoNormal"><span style="color:black"> </span></p><p class="MsoNormal"><span style="color:black">If this is a reasonable proposal to go forward, I will submit a blueprint & follow-up with implementation.</span></p>
<p class="MsoNormal"><span style="color:black"> </span></p><p class="MsoNormal"><span style="color:black">Thanks.</span></p><p class="MsoNormal"><span style="color:black"> </span></p><p class="MsoNormal"><span style="color:black">--Shyam</span></p>
</div></div><p class="MsoNormal"><span style="font-size:10.5pt;color:black">_______________________________________________ Mailing list: <a href="https://launchpad.net/~openstack">https://launchpad.net/~openstack</a> Post to : <a href="mailto:openstack@lists.launchpad.net">openstack@lists.launchpad.net</a> Unsubscribe : <a href="https://launchpad.net/~openstack">https://launchpad.net/~openstack</a> More help : <a href="https://help.launchpad.net/ListHelp">https://help.launchpad.net/ListHelp</a> </span></p>
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