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<p class="MsoNormal"><span style="color:black">Hello Community,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">We’ve hit a rather pesky bug that I’m hoping someone else has seen before. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">We have an issue with Nova where a set of Cinder backed VMs are having their XML definitions modified after a live migration. Specifically, the destination host ends up having the disk type changed from ‘qcow2’
to ‘raw’. This ends up with the VM becoming unbootable upon the next hard reboot (or nova stop/start is issued). The required fix ATM is for us to destroy the VM and recreate from the persistent Cinder volume. Clearly this isn’t a maintainable solution as
we rely on live migration for patching infrastructure.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Any thoughts, ideas, would be most welcome. Gory details are below.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Here’s the key details we have:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoNormal" style="color:black;mso-list:l0 level1 lfo1">Nova boot an instance from the existing volume works as expected.<o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l0 level1 lfo1">After live migration the ‘type’ field in the virsh XML is changed from ‘qcow2’ -> ‘raw’ and we get a ‘No bootable device’ from the VM (rightly so)<o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l0 level1 lfo1">After reverting this field automatically (scripted solution), a ‘nova stop’ followed by a ‘nova start’ yet again rewrites the XML with the bad type=’raw’. <o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l0 level1 lfo1">It should be noted that before a live migration is performed ‘nova stop/start’ functions as expected, no XML changes are written to the virsh definition.<o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l0 level1 lfo1">Injecting additional logs into the python on these two hosts I’ve narrowed it down to ‘bdm_info.connection_info’ on the destination end is choosing the ‘raw’ parameter somehow (I’ve only got
so far through the code at this time). The etree.XMLParser of the source hypervisors XML definition is properly parsing out ‘qcow2’ type.<o:p></o:p></li></ul>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Some background info:<o:p></o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoNormal" style="color:black;mso-list:l2 level1 lfo2">We’re currently running the Wallaby release with the latest patches. <o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l2 level1 lfo2">Hybrid OS (Stream8 /Rocky 8) on underlying hardware with the majority of the Control Plane Stream aside from our Neutron Network Nodes. Computes are roughly split 50/50 Stream/Rocky.<o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l2 level1 lfo2">The Cinder volumes that experience this were copied in from a previous OpenStack cloud (Pike/Queens) on the backend. I.e. NetApp snapmirror, new bootable Cinder volume created on the backend,
and an internal NetApp operation for a zero copy operation over the backing Cinder file. <o:p></o:p></li><ul style="margin-top:0in" type="circle">
<li class="MsoNormal" style="color:black;mso-list:l2 level2 lfo2">Other Cinder volumes that don’t exhibit this to mostly be in ‘raw’ format already (we haven’t vetted every single bootable Cinder volume yet).<o:p></o:p></li></ul>
<li class="MsoNormal" style="color:black;mso-list:l2 level1 lfo2">We’ve noticed these Cinder volumes lack some metadata fields that other Cinder volumes create by Glance have (more details below).<o:p></o:p></li></ul>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Ideas we’ve tried:<o:p></o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoNormal" style="color:black;mso-list:l1 level1 lfo3">Adjusting settings on both computes for ‘use_cow_images’ and ‘force_raw_images’ seem to have zero effect.<o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l1 level1 lfo3">Manually setting the Cinder metadata parameters to no avail (i.e. openstack volume set --image-property disk_format=qcow2).<o:p></o:p></li></ul>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks!<o:p></o:p></p>
<p class="MsoNormal">-Robert<o:p></o:p></p>
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