On 06/23/2018 08:38 AM, Volodymyr Litovka wrote:
Dear friends,
I did some tests with making volume available without stopping VM. I'm using
CEPH and these steps produce the following results:
1) openstack volume set --state available [UUID]
- nothing changed inside both VM (volume is still connected) and CEPH
2) openstack volume set --size [new size] --state in-use [UUID]
- nothing changed inside VM (volume is still connected and has an old size)
- size of CEPH volume changed to the new value
3) during these operations I was copying a lot of data from external source and
all md5 sums are the same on both VM and source
4) changes on VM happens upon any kind of power-cycle (e.g. reboot (either soft
or hard): openstack server reboot [--hard] [VM uuid] )
- note: NOT after 'reboot' from inside VM
It seems, that all these manipilations with cinder just update internal
parameters of cinder/CEPH subsystems, without immediate effect for VMs. Is it
safe to use this mechanism in this particular environent (e.g. CEPH as backend)?
There are a different set of instructions[1] which imply that the change should
be done via the hypervisor, and that the guest will then see the changes
immediately.
Also, If you resize the backend in a way that bypasses nova, I think it will
result in the placement data being wrong. (At least temporarily.)
Chris
[1]
https://wiki.skytech.dk/index.php/Ceph_-_howto,_rbd,_lvm,_cluster#Online_resizing_of_KVM_images_.28rbd.29
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