Lync front end service not starting on Lync2013

Troubles after migrating from 2010 tol 2013?
Just finishing rebuilding a lync topologi after migrating from a lync 2010 toa 2013 pool.
After moving CMS and dedeploying 2010 none of the front end servers wolud start.
The front end service just reported "starting".



If you see error like this in the eventviewer on the front end you migh be in for some serious work hours.

Currently waiting for routing group: {F6652B7B-81AF-5398-B34B-045EDCCDC31C}.

Number of groups potentially not yet placed: 14.

Total number of groups: 14.

And this was caused by invalid sip-uri in the user pool.

The RtcDb Sync Agent has encountered an Exception: [System.Data.SqlClient.SqlException (0x80131904): XML parsing: line 1, character 36426, semicolon expected

We have spent about a week rebuilding this together with Microsoft.

The issue boiled down to only having two front end servers in a pool and also a ocscore CU1 update that generated.

I could find this on the web about two front end servers:

Can I have a Front End pool with 2 servers ?

Yes you can, though Microsoft do not recommend it. Why ? (Deja vu…. Wasn’t this the question I started this blog entry with ?  )

A Front End pool with 2 servers will work perfectly fine, but admin’s remember the following

 1. You have only one replica of the database (primary and secondary) and thus do not satisfy the underlying windows fabric model of 3 database copies.

2. The pool will continue to function normally if only a single server is restarted at any one time.

3. If both servers are taken / went offline at the same time – there is a good chance that when they come back on, they might get the incorrect node id as mentioned above and service would not start. In this situation, perform one of the 2 steps mentioned above and you are good to go.

Even better – can I have a Front End pool with just 1 server ?

Yes you can though not recommended as you will have to run the Reset-CsPoolRegistrarState every time you restart the server. This is because, during every restart, the quorum will inform the server that there are no secondary databases available and will then shut down services. But once services are up and running, it will continue to run until the next restart.

Other than getting one foot in the Enterprise Pool world, there is no advantage what so ever in running a single server EE pool and hence a better suggestion / option is to install a standard edition server instead.

Hope I didn’t make it too complicated – because, once I got my head around ‘why’, it became easier at least to explain the process / reasons to clients in workshops so that they can make  an informed decision.