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Yes, with Cinder resize works, and volume resize is separated function. 
But my issue is when I use VM boot from image, without using cinder, 
using CEPH directly in nova.

On 2016.02.10. 16:49, Alberto Molina Coballes wrote:
> Sorry Mārtiņš, my previous comment wasn't completely correct.
>
> I'm assuming that you're using Ceph as a cinder backend and using
> instances with the root filesystem defined in a volume, so you want
> to resize your instances without modify the size of the volume, just
> modify RAM and vCPU, right?
>
> In that case you can define several flavors with 0 GiB of disk size
> and resize up and down your instances between these flavors, but not
> with other flavors with a disk size greater than 0 GiB defined.
>
> Regards,
>
> Alberto