Open Stack

On Wed, Oct 12, 2016 at 9:59 PM, Giulio Fidente <gfidente at redhat.com> wrote:

> On 10/12/2016 02:29 PM, Thiago da Silva wrote:
>
>>
>>
>> On 10/12/2016 07:10 AM, Giulio Fidente wrote:
>>
>>> hi,
>>>
>>> we introduced support for the deployment of Ceph in the liberty
>>> release so that it could optionally be used as backend for one or more
>>> of Cinder, Glance, Nova and more recently Gnocchi.
>>>
>>> We used to deploy Ceph MONs on the controller nodes and Ceph OSDs on
>>> dedicated ceph-storage nodes so a deployment of OpenStack with Ceph
>>> would need at least 1 more additional node to host a Ceph OSD.
>>>
>>> In our HA scenario the storage backends are configured as follows:
>>>
>>> Glance -> Swift
>>> Nova (ephemeral) -> Local
>>> Cinder (persistent) -> LVM (on controllers)
>>> Gnocchi -> Swift
>>>
>>> The downside of the above configuration is that Cinder volumes can not
>>> be replicated across the controller nodes and become unavailable if a
>>> controller fails, while production environments generally expect
>>> persistent storage to be highly available. Cinder volumes instead
>>> could even get lost completely in case of a permanent failure of a
>>> controller.
>>>
>>> With the Newton release and the composable roles we can now deploy
>>> Ceph OSDs on the compute nodes, removing the requirement we had for an
>>> additional node to host a Ceph OSD.
>>>
>>> I would like to ask for some feedback on the possibility of deploying
>>> Ceph by default in the HA scenario and use it as backend for Cinder.
>>>
>>> Also using Swift as backend for Glance and Gnocchi is enough to cover
>>> the availability issue for the data, but it also means we're storing
>>> that data on the controller nodes which might or might not be wanted;
>>> I don't see a strong reason for defaulting them to Ceph, but it might
>>> make more sense when Ceph is available; feedback about this would be
>>> appreciated as well.
>>>
>> I think it would be important to take into account the recently created
>> guiding principles [0]:
>>
>> "While the software that OpenStack produces has well defined and
>> documented APIs, the primary output of OpenStack is software, not API
>> definitions. We expect people who say they run “OpenStack” to run the
>> software produced by and in the community, rather than alternative
>> implementations of the API."
>>
>> In the case of Cinder, I think the situation is a bit muddy as LVM is
>> not openstack software, and my limited understanding is that LVM is used
>> as a reference implementation, but in the case of Swift, I think RGW
>> would be considered an 'alternative implementation of the API'.
>>
>> Thiago
>>
>
> hi Thiago,
>
> sorry if it wasn't clear in my original message but I did not suggest to
> replace Swift with Ceph RGW.
>
> Swift would continue to be deployed by default, not RGW.
>

RGW utilizes Swift. So Swift has to be there anyway -;


>
> The feedback I'm asking for is about storing (or not) the Cinder volumes
> in Ceph for the HA scenario by default, and also store the Glance images
> and Gnocchi metrics in Ceph or rather keep that data in Swift.
> --
> Giulio Fidente
> GPG KEY: 08D733BA
>
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-- 
Email:
shinobu at linux.com
shinobu at redhat.com
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