[openstack-dev] [Spam] Re: [Openstack][TripleO] [Ironic] What if undercloud machines down, can we reboot overcloud machines?

Clint Byrum clint at fewbar.com
Thu Aug 28 15:58:11 UTC 2014


Excerpts from Jyoti Ranjan's message of 2014-08-27 21:20:19 -0700:
> I do agree but it create an extra requirement for Undercloud if we high
> availability is important criteria. Because of this, undercloud has to be
> there 24x7, 365 days and to make it available we need to have HA for this
> also. So, you indirectly mean that undercloud also should be designed
> keeping high availability in mind.

I'm worried that you may be overstating the needs of a typical cloud.

The undercloud needs to be able to reach a state of availability when
you need to boot boxes. Even if you are doing CD and _constantly_
rebooting boxes, you can take your undercloud down for an hour, as long
as it can be brought back up for emergencies.

However, Ironic has already been designed this way. I believe that
Ironic has a nice dynamic hash ring of server ownership, and if you
mark a conductor down, the other conductors will assume ownership of
the machines that it was holding. So the path to making this HA is
basically "add one more undercloud server."

Ironic experts, please tell me this is true, and not just something I
inserted into my own distorted version of reality to help me sleep at
night.



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