Database replication between different cluster !!!

Unanswered Question
May 23rd, 2010

Hi all,

I have two different clusters located in two different location, each cluster has one node ... one cluster has cucm vers 6.1.2 & other cluster has ver 6.1.4 the connection between both the cluster is via Leased Line .. I want to replicate the database of both clusters, can any body tell me how to replicate database between different clusters ???


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Overall Rating: 4.5 (2 ratings)
William Bell Sun, 05/23/2010 - 11:20

The database cannot be replicated between clusters.  Replication can only occur between member nodes on the same cluster.  What specifically did you want to "replicate"?




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anis_cisco Mon, 05/24/2010 - 10:41

hi william,

Thanks for your reply... actually i want to use Extension Mobility & Cisco Unified Presence for both sites !!! if i can replicate database then i can configure EM & users can access the system either they are in Site A or Site B same as for Cisco Presence !!!!!

if i cant replicate the database between clusters so it means i have make nodes & i have to do re-installation from scratch ???


David Hailey Mon, 05/24/2010 - 11:14

This is cut and dry as Bill said.  You cannot replicate data between 2 separate clusters.  If you want Cross Cluster Extension Mobility - this feature is available/coming in CUCM 8x.  I would not recommend an 8.0 release unless there is a feature that you MUST have.  So, with that said -  Bill is correct, cannot replicate between clusters.  If this dampers your requirements, then you may need to reconsider your architecture and, in particular, your clustering model.  As far as presence goes, do you mean basic CUCM presence or presence using a CUPS server?

Jaime Valencia Mon, 05/24/2010 - 11:45

In case you're interested in doing just 1 cluster then the answer is yes, you need to reinstall the servers to join another cluster, but also to have your licenses rehosted to the other cluster.

Also bear in mind the requirements for this deployment models:

Clustering Over the IP WAN

The other option is as mentioned, keep 2 clusters and use BAT. This obviously means any change will need to be manually replicated in the other cluster.



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David Hailey Mon, 05/24/2010 - 13:25

Lesson learned for you is that these are the types of design level requirements that need to be flushed out BEFORE you implement anything.

anis_cisco Wed, 06/02/2010 - 14:36


I got to know that i can use Cisco Unified Application Environment for the database replication b/w different clusters ???? is it possible ???

one thing about CUCM ver 8 ... i can run Extension Mobility between different clusters but can i replicate complete database in vers 8.0 ???


Jaime Valencia Wed, 06/02/2010 - 15:55

I dont' know about Cisco Unified Application Environment being able to do that, I doubt it can. You'd need to dig into the documentation to confirm that.

8.X doesn't exchange the DB, it just exchanges the necessary information about your UDP and only exists when you use it on a remote cluster.

CUCM doesn't provide this capability in any version and very unlikely will ever do. If you want to share a common DB you need to configure just 1 cluster as already explained.



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David Hailey Wed, 06/02/2010 - 17:32

Just to build on Java's last statement and your persistence on this in general:

If this can be done via CUAE, I assure you that it is not cut and dry nor would it likely be desirable to replicate the entire database between 2 clusters.  For one, there would definitely be licensing ramifications (e.g., DLU's consumed by devices replicated into the database of one cluster that actually exist on another cluster, not the local one) and two, there would be some performance hit at a certain point as well.  If you replicated the entire database, you would get more than directory and UDP data.  You would get phones, route patterns, translations, CSS, PT, etc...all of this adds up to a "weight" within the database which, based on your platform, can ultimately lead to slower processing and performance.  It may not be as bad on the Linux platform as the previous Windows but having helped to build and administer a near 12,000+ user "supercluster" - it is something you must be cognizant of.

CUCM 8x has cross-cluster extension mobility and it does not replicate the entire database to do this.  I haven't looked at the cross-cluster feature functions in-depth but the bulk of the feature probably has little to do with replication.  I could be wrong on that...not something I've had much need to look at recently.  I also don't think replicating the database between clusters would be a supported or necessary feature for the reasons listed above as well as others.


Jaime Valencia Wed, 06/02/2010 - 18:08

Just to expand a little bit on this

Hailey is indeed right on the fact that EMCC has little to do with DB replication, and while speaking of DLU/licensing issues, EMCC doesn't consume DLUs precisely to avoid that kind of issues that would arise if you already are using 100% of your DLUs and use the feature:

DLUs are not consumed in the home  cluster for the registered visiting phones.

The feature relies on the EM service to get the info from the UDP.

The EM service in the visiting cluster attempts to  locate the home cluster of the user by sending out queries to each of  the EMCC remote clusters that have been configured in Unified CM. When  the user's home cluster responds positively, this initiates  communications between the EM services of both clusters to exchange  information that essentially brings the device information into the home  cluster database and allows the home cluster to build a configuration  file for this visiting phone. This configuration file incorporates some  device configuration from the visiting cluster, configuration parameters  from the home cluster, and the user's device profile in the home  cluster.

But the profile that is created is not stored permanently in the DB of the visiting cluster, once you log out, the info is removed from the DB.

The services involved in DB replication are never invoked by EMCC.

I'd strongly recommend to look into a re-design of what you have and move forward. There must be other way to achieve what you want that doesn't involve trying to replicate the whole DB between clusters.

DB replication is only between members of the cluster.



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Harmit Singh Sun, 05/23/2010 - 21:38


Like Willliam said, it is not possible. What is the objective? If there is certain data that needs to be migrated to the other cluster, can it not be achieved via BAT?




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