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Hi,

>> yes so the evacutate api however should not be assumed to preserve data.
>>   orginally it did not unless you mounted the nova instnace dir on nfs,
 >> latter support for preserving cinder volumes was added to the libvirt
driver but by defalut
>> you shoudl assume that that instnace are rebuilt with a fresh image as
that is the default behavior
>>   if virt drivers dont opt in to preserving it.

>>   strictly speakign the libvirt virt driver could decide to reimage the
cinder volumes if it chose too but that is more work and would be
>>   a worse user experence so we are never going to regess this but wether
data is preserved is entirely dirver dependent.

Got it. I am using cinder backed volumes for my instances only in
production. But Openstack Trove deploy root volume of database instance on
instance directory on compute host. I am looking the way to preserve its
data. May b mounting it on NFS is a way.

$ nova host-evacuate is the advised way to recover instances (cinder backed
only) with preserving data from failed host or any other way ?

Ammad

On Tue, Jul 27, 2021 at 4:12 PM Sean Mooney <smooney at redhat.com> wrote:

> On Tue, 2021-07-27 at 10:29 +0100, Lee Yarwood wrote:
> > On Tue, 27 Jul 2021 at 08:12, Ammad Syed <syedammad83 at gmail.com> wrote:
> > >
> > > Hi,
> > >
> > > I am using openstack wallaby. I am testing to evacuate instances from
> failed host.
> > >
> > > The feature works fine. The instances on cinder backed shared storage
> rebuild on other host and their data is preserved. However the instances
> that are on local compute storage rebuild with fresh image on other host
> and data on root disk was lost.
> yes so the evacutate api however should not be assumed to preserve data.
> orginally it did not unless you mounted the nova instnace dir on nfs,
>  latter support for preserving cinder volumes was added to the libvirt
> driver but by defalut
> you shoudl assume that that instnace are rebuilt with a fresh image as
> that is the default behavior
> if virt drivers dont opt in to preserving it.
>
> strictly speakign the libvirt virt driver could decide to reimage the
> cinder volumes if it chose too but that is more work and would be
> a worse user experence so we are never going to regess this but wether
> data is preserved is entirely dirver dependent.
>
> > >
> > > The question is, is it possible to evacuate all instances from failed
> host that are on shared storage only ?
> > >
> > > Ammad
> >
> > No but that's a valid feature request IMHO, the current API is defined
> below:
> >
> >
> https://docs.openstack.org/api-ref/compute/?expanded=evacuate-server-evacuate-action-detail#evacuate-server-evacuate-action
>
> what woudl it look like. woudl we reust the old onSharedStorage flag in a
> new micorverion to mean evauate only if ion shared storage?
> i think it might be more useful to extend the server show to contain if
> the server is on shared sotrage and then leave it up to the client
> to evaucate the node or not.
>
> i dont really think we shoudl be extendeing the nova clinet host-evacuate
> commnad at this point since we are not gong to prot tha tot osc and
> evenutally
> the nova client cli should be removed. i dont think we have formally
> deprecated or feature frozen nova client yet but since stephen updated osc
> to have
> parity now i think we shoudl dicuss at the ptg is it time to deprecate it
> in yoga(just the cli part until sdk has partiy).
>
> > Cheers,
> >
> > Lee
> >
> >
>
>
>

-- 
Regards,


Syed Ammad Ali
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