[cinder][nova] Migrating servers' root block devices from a cinder backend to another

Jean-Philippe Méthot jp.methot at planethoster.info
Thu Jan 30 15:23:40 UTC 2020


To follow up on my last email, I have tested the following hackaround in my testing environment:

>> 
>> Assuming you're using the Libvirt driver, a hackaround here is to cold
>> migrate the instance to another host, this refreshes the connection_info
>> from c-api and should allow the instance to boot correctly.
>> 

I can confirm that on OpenStack Queens, this doesn’t work. Openstack can’t find the attachment ID as it was marked as deleted in the cinder DB. I’m guessing it put itself as deleted when I did  cinder reset-state --attach-status detached b70b254f-58cd-4940-b976-6f4dc0209a8c.
Even though I did cinder reset-state --attach-status attached  b70b254f-58cd-4940-b976-6f4dc0209a8c, the original attachment ID did not undelete itself. It also didn’t update itself to the new path. As a result, nova seems to be looking for the attachment ID when trying to migrate and errors out when it can’t find it.

That said, I do remember using this workaround in the past on older versions of Openstack, so this definitely used to work. I guess a change in cinder probably broke this.

Jean-Philippe Méthot
Openstack system administrator
Administrateur système Openstack
PlanetHoster inc.
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