Open Stack

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)?

 From practical point of view, it's useful when somebody, for example, 
update project in batch mode, and will then manually reboot every VM, 
affected by the update, in appropriate time with minimized downtime 
(it's just reboot, not manual stop/update/start).

Thank you.

-- 
Volodymyr Litovka
   "Vision without Execution is Hallucination." -- Thomas Edison