[openstack-dev] [cinder] making volume available without stopping VM

Sean McGinnis sean.mcginnis at gmx.com
Mon Jun 25 18:42:48 UTC 2018


> 
> In fact, I'm ok with delayed resize (upon power-cycle), and it's not an
> issue for me that VM don't detect changes immediately. What I want to
> understand is that changes to Cinder (and, thus, underlying changes to CEPH)
> are safe for VM while it's in active state.
> 

No, this is not considered safe. You are forcing the volume state to be
availabile when it is in fact not.

Not sure if it's an option for you, but in the Pike release support was added
to be able to extend attached volumes. There are several caveats with this
feature though. I believe it only works with libvirt, and if I remember right,
only newer versions of libvirt. You need to have notifications working for Nova
to pick up that Cinder has extended the volume.

You can get some details from the cinder spec:

https://specs.openstack.org/openstack/cinder-specs/specs/pike/extend-attached-volume.html

And the corresponding Nova spec:

http://specs.openstack.org/openstack/nova-specs/specs/pike/implemented/nova-support-attached-volume-extend.html

You may also want to read through the mailing list thread if you want to get in
to some of the nitty gritty details behind why certain design choices were
made:

http://lists.openstack.org/pipermail/openstack-dev/2017-April/115292.html



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