[openstack-dev] [nova] Do any hyperviors allow disk reduction as part of resize ?

Aryeh Friedman aryeh.friedman at gmail.com
Fri Jun 13 10:12:16 UTC 2014


Theoretically impossible to reduce disk unless you have some really nasty
guest additions.


On Fri, Jun 13, 2014 at 6:02 AM, Day, Phil <philip.day at hp.com> wrote:

>  Hi Folks,
>
>
>
> I was looking at the resize code in libvirt, and it has checks which raise
> an exception if the target root or ephemeral disks are smaller than the
> current ones – which seems fair enough I guess (you can’t drop arbitary
> disk content on resize), except that the  because the check is in the virt
> driver the effect is to just ignore the request (the instance remains
> active rather than going to resize-verify).
>
>
>
> It made me wonder if there were any hypervisors that actually allow this,
> and if not wouldn’t it be better to move the check to the API layer so that
> the request can be failed rather than silently ignored ?
>
>
>
> As far as I can see:
>
>
>
> baremetal: Doesn’t support resize
>
>
>
> hyperv: Checks only for root disk (
> https://github.com/openstack/nova/blob/master/nova/virt/hyperv/migrationops.py#L99-L108
>  )
>
>
>
> libvirt:     fails for a reduction of either root or ephemeral  (
> https://github.com/openstack/nova/blob/master/nova/virt/libvirt/driver.py#L4918-L4923
> )
>
>
>
> vmware:   doesn’t seem to check at all ?
>
>
>
> xen: Allows resize down for root but not for ephemeral (
> https://github.com/openstack/nova/blob/master/nova/virt/xenapi/vmops.py#L1015-L1032
> )
>
>
>
>
>
> It feels kind of clumsy to have such a wide variation of behavior across
> the drivers, and to have the check performed only in the driver ?
>
>
>
> Phil
>
>
>
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>
>


-- 
Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org
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