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Hi all,



2014-04-03 18:47 GMT+02:00 Meghal Gosalia <meghal at yahoo-inc.com>:

>  Hello folks,
>
>  Here is the bug [1] which is currently not allowing a host to be part of
> two availability zones.
> This bug was targeted for havana.
>
>  The fix in the bug was made because it was assumed
> that openstack does not support adding hosts to two zones by design.
>
>  The assumption was based on the fact that ---
> if hostX is added to zoneA as well as zoneB,
> and if you boot a vm vmY passing zoneB in boot params,
> nova show vmY still returns zoneA.
>
>  In my opinion, we should fix the case of nova show
> rather than changing aggregate api to not allow addition of hosts to
> multiple zones.
>
>  I have added my comments in comments #7 and #9 on that bug.
>
>  Thanks,
> Meghal
>
>
 [1] Bug - https://bugs.launchpad.net/nova/+bug/1196893
>
>
>


Thanks for the pointer, now I see why the API is preventing host to be
added to a 2nd aggregated if there is a different AZ. Unfortunately, this
patch missed the fact that aggregates metadata can be modified once the
aggregate is created, so we should add a check when updating metadate in
order to cover all corner cases.

So, IMHO, it's worth providing a patch for API consistency so as we enforce
the fact that a host should be in only one AZ (but possibly 2 or more
aggregates) and see how we can propose to user ability to provide 2
distincts AZs when booting.

Does everyone agree ?

-Sylvain


>   On Apr 3, 2014, at 9:05 AM, Steve Gordon <sgordon at redhat.com> wrote:
>
> ----- Original Message -----
>
> Currently host aggregates are quite general, but the only ways for an
> end-user to make use of them are:
>
> 1) By making the host aggregate an availability zones (where each host
> is only supposed to be in one availability zone) and selecting it at
> instance creation time.
>
> 2) By booting the instance using a flavor with appropriate metadata
> (which can only be set up by admin).
>
>
> I would like to see more flexibility available to the end-user, so I
> think we should either:
>
> A) Allow hosts to be part of more than one availability zone (and allow
> selection of multiple availability zones when booting an instance), or
>
>
> While changing to allow hosts to be in multiple AZs changes the concept
> from an operator/user point of view I do think the idea of being able to
> specify multiple AZs when booting an instance makes sense and would be a
> nice enhancement for users working with multi-AZ environments - "I'm OK
> with this instance running in AZ1 and AZ2, but not AZ*".
>
> -Steve
>
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