Unregistering a domain from UCS Central in a disaster

[mdrudge]

Hello all,

We use UCS Central extensively, and our Prod and DR domains are using the same instance for configuration management.  I'm trying to think of the best way to deal with the case if our DR site could not communicate with our UCS Central in a DR situation.  I know that if there's no change in the hardware, there shouldn't be an issue, but what if we need to configure new hosts in our DR site during such a disaster?  I'm thinking that our best bet is to unregister the DR site from UCS Central, and localize all the service profiles, templates, and pools.  Then we will never be able to use UCS Central again for our DR domain, since there will be conflicts with the newly-localized global settings.  Am I understanding how this works correctly?  Will all the current settings applied on the domain then be kept without interruption, and we can use those templates for configuring new blades, etc. from UCSM?  Also, in the case of Deep Remove global, all the servers will have to go down, and then all the global settings re-created in UCSM, with servers non-functional until those settings are re-created, correct?  I'm just trying to make sure I have my understanding correct.  What are some thoughts?  Thanks!

[Tapper · Accepted solution]

We have the same setup where our Production and DR site use the same UCS Central.  Since UCS Central is a VMware appliance, we have it on replicated storage to our DR site.  So in case of a DR, we will just add the UCS Central to our DR site vCenter.  Then console into it and change the IP for UCS Central.  Then change the DNS entry to match that new IP.  Then we can reverse this process when our Production site comes back up.  This will work as long as you have all of your UCS Domains registered to UCS Central by name, not IP.  If you do have them registered by name, there are a few simple command lines to get that changed to name.

I hope this helps you out.  Let me know if you have any questions.

[mdrudge]

Thanks for this, it makes total sense!  Unfortunately, the DR domain is registered via IP.  I'm kicking myself for doing an in-place upgrade of the FIs in DR, instead of migrating chassis to a new domain piecemeal, like I did in prod.  The registration is legacy from before I started, and the rest of our domains use names.  I guess that's a big piece of information I missed mentioning.  I do appreciate this, it gives me an idea of how it works if we had it registered properly.  At some point I may be able to do this in this way, if we have a chance to upgrade FIs again in the next few years, although we'll probably be using Intersight from the cloud by then haha.

In the meantime, it's still looking like I need to pull the DR domain out of Central permanently if there is a disaster.  

[Tapper]

You can change the registration of UCS Manager in UCS Central from IP to FQDN.  I have done it on 3 of my domains without any impact.  You will need to get the debug plugin from TAC. Just open a case and they can help you.  Takes less than 5 minutes.  

Let me know if you have questions.

[mdrudge]

Oh wow, yeah I thought I was SOL.  And I just noticed the last sentence of your first response, where you mentioned that it could be changed.  I'm familiar with the debug plugin.  I will have to make this part of my plan.  Thanks!