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Hi Jay,

> We have had similar issues with extending attached volumes that are 
> iSCSI based. In that case the VM has to be forced to rescan the scsi bus.
>
> In this case I am not sure if there needs to be a change to Libvirt or 
> to rbd or something else.
>
> I would recommend reaching out to John Bernard for help.

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.

Hopefully, Jon will help with this question.

Thank you!

On 6/23/18 8:41 PM, Jay Bryant wrote:
>
>
> On Sat, Jun 23, 2018, 9:39 AM Volodymyr Litovka <doka.ua at gmx.com 
> <mailto:doka.ua at gmx.com>> 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)?
>
>      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
>

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

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