Open Stack

On Mon, 2022-01-24 at 10:59 +0100, Christian Rohmann wrote:
> Hey Mohammed,
> 
> 
> thanks for the input!
> 
> On 21/01/2022 12:48, Mohammed Naser wrote:
> > Sorry to hijack such an old thread. Looking into these features, I was 
> > just wondering if it was possible to:
> > 
> > 
> >       1) Disable the support for pause / suspend altogether and not
> >     allow anyone to place instances in such states?
> > 
> > you can use policy to disable suspending vms via the api
> 
> Good point, thanks.
> 
> 
> >       2) Change the storage location of the saved guest RAM to a
> >     shared storage to allow the instance to be migrated while being
> >     suspended/paused. As far as I can see currently this data is saved
> >     on the host disk.
> > 
> > you can mount the path where things get saved at where ever you want 
> > (I think it’s somewhere inside /var/lib/nova/instances)
> 
> 
> That's true, but this would require some multi-mountable shared storage 
> like CephFS or some NFS to remove the dependency from a single node.
> It's not like Nova would store this data as e.g. a RBD image in Ceph via 
> some config option, right?

the instance state dir contence no.
so wehn you use the rbd images backend and you suspend the ram is saved to disk on the local system
i could see adding a feature to nova to poteally upload that as an addtional rbd image to ceph.
or maybe store it itn swift or something like that but nova cannot do it today.

you could certenly put the instance state dir on a cephfs share or nfs
we dont realy like dealing with shared storage for the state dir but the generic code we have for nfs
should work with cephfs. just be aware de dont currently test that but i dont see why we could not
extned the ceph job to mount /var/lib/nova on cephfs to get coverage in the ci.


in the short term i agree that using a cephfs mount is likely the best way to avoid the guest ram from beign stored
on the comptue node disk.  in terms fo disabling suspend the simplelst way to do that is to alter the policy.json
and make that either admin only or preferably require a new role then just dont give that role to your tenants.

> 
> 
> 
> Regards
> 
> 
> Christian
> 
>