From: <Baldassin>, Santiago B 
<santiago.b.baldas...@intel.com<mailto:santiago.b.baldas...@intel.com>>
Reply-To: "OpenStack Development Mailing List (not for usage questions)" 
<openstack-dev@lists.openstack.org<mailto:openstack-dev@lists.openstack.org>>
Date: Wednesday, March 26, 2014 at 5:17 AM
To: "OpenStack Development Mailing List (not for usage questions)" 
<openstack-dev@lists.openstack.org<mailto:openstack-dev@lists.openstack.org>>
Subject: Re: [openstack-dev] [nova][scheduler] Availability Zones and Host 
aggregates..

I would say that the requirement is not valid. A host aggregate con only have 
one availability zone so what you actually can have is a compute node that’s 
part of 2 host aggregates, which actually have the same availability zone.

It is in our case where we have a superset host aggregate that has all the 
hosts and then we have subset host aggregates(AZ) based on PDU. Need is that 
our user can specify the AZ based on the PDU but also in case no AZ is 
specified we want to load balance from the superset which contains two 
host-aggregates(AZ).


In the scenario you mentioned below where you create the aggregates without 
associating the availability zone, after updating the aggregates with the 
zones, the hosts still share the same availability zone right?

No the host becomes part of two availability zones one for each of the host 
aggregates.

From: John Garbutt [mailto:j...@johngarbutt.com]
Sent: Wednesday, March 26, 2014 8:47 AM
To: OpenStack Development Mailing List
Subject: Re: [openstack-dev] [nova][scheduler] Availability Zones and Host 
aggregates..


Sounds like an extra weighter to try and balance load between your two AZs 
might be a nicer way to go.

The easiest way might be via cells, one for each AZ . But not sure we merged 
that support yet. But there are patches for that.

John
On 25 Mar 2014 20:53, "Sangeeta Singh" 
<sin...@yahoo-inc.com<mailto:sin...@yahoo-inc.com>> wrote:
Hi,

The availability Zones filter states that theoretically a compute node can be 
part of multiple availability zones. I have a requirement where I need to make 
a compute node part to 2 AZ. When I try to create a host aggregates with AZ I 
can not add the node in two host aggregates that have AZ defined. However if I 
create a host aggregate without associating an AZ then I can add the compute 
nodes to it. After doing that I can update the host-aggregate an associate an 
AZ. This looks like a bug.

I can see the compute node to be listed in the 2 AZ with the 
availability-zone-list command.

The problem that I have is that I can still not boot a VM on the compute node 
when I do not specify the AZ in the command though I have set the default 
availability zone and the default schedule zone in nova.conf.

I get the error “ERROR: The requested availability zone is not available”

What I am  trying to achieve is have two AZ that the user can select during the 
boot but then have a default AZ which has the HV from both AZ1 AND AZ2 so that 
when the user does not specify any AZ in the boot command I scatter my VM on 
both the AZ in a balanced way.

Any pointers.

Thanks,
Sangeeta

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