resize a vm to a flavor with pci-passthrough

Sean Mooney smooney at
Mon Apr 8 10:24:56 UTC 2019

On Mon, 2019-04-08 at 05:45 +0000, Manuel Sopena Ballesteros wrote:
> Dear Openstack community,
> I have 1 physical node with x4 nvidia nv100 running 1 fat vm. Additionally I am adding a nvme drive into that host and
> I would like to attach the nvme drive to the vm. Ideally I prefer to avoid data migration and redeploy the software.
> My problem is that I don't have another host with gpus so I am guessing that the vm can't be migrated. Am I right
> assuming this?
we do have a config option to allow same host resize however in your case it likely still wont work.

when we do a resize to a new flavor we need to temporaily claim both the existing resouce for the currnt flavor and the
new resouces for the target flavor. so unless you have 8 gpus on that system it will fail.
you could try shelving the vm. resizing and unshelving. but really there is no good option here.

> So far I thought about 2 possibilities but I don't know whether they would work:
> Option 1: crate a new flavor with the pci device pass-through and resize existing vm (I hope the new vm with the new
> flavor will have the nvme attached).
if you have enough space for the new flavor then yes that should work.
> Option 2: convert ephemeral virtual disk into a bootable volume. Destroy vm. Create new vm with the new volume as a
> boot device.
if all the data you want to keep is in the root disk then a snapshot will work but this would evffectivly be the
same as the shelve resize unselve workflow i suggested above. if you have addtional ephemeral disk beyond the
root disk then you should backup all the data to a cinder volume manually first. then recreate the vm and attach those
> Which option would be preferred? Is there any other think I can do?
> Thank you very much
> Manuel
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