You can’t collocate Lync Server 2013 enterprise pool database with Lync Server 2010 on separate SQL instances

I originally thought I could get away with collocating a Lync Server 2013 enterprise pool with a Lync Server 2010 enterprise pool SQL server, by installing a new instance on the SQL Server that hosts our current Lync Server 2010 enterprise SQL database during the transition period over to the new pool but then I noticed that I am unable to create or select it if I define it prior to creating the new pool.  The phrasing of this issue I have is a bit confusing so let me itemized the situation in point form to better explain what I’m trying to do.

Lync Server 2010 Database Server – SVR-SQL-04.domain.local
Lync Server 2010 Database Instance – Default
Lync Server 2010 Database Server – SVR-SQL-04.domain.local
Lync Server 2010 Database Instance – Lync2013

What I’m basically trying to do is to have multiple SQL Server Standard instances on the same Windows 2008 R2 Server to hosts the databases for both pools but when I try to create the new data store during the creation of the Lync Server 2013 pool, I receive the following warning:

SQL Server ‘svr-sql-04.domain.local’ already contains a SQL instance hosting role ‘UserStore’.

I’ve also tried defining the store first as such:

Which allows me to define the store:

… but still doesn’t allow me to select it during the enterprise front end pool deployment:

After browsing around the documentation on TechNet, I finally found the following snippet:

You must use separate and distinct computers running Microsoft SQL Server 2008 R2 or Microsoft SQL Server 2012 for your Lync Server 2013 database instances. You cannot use the same instance of SQL Server for a Lync Server 2013 Front End pool that you use for a Lync Server 2010 or Office Communications Server 2007 R2 Front End pool. If you define and configure Lync Server 2013 in Topology Builder for a deployment that already has Lync Server 2010 or Office Communications Server 2007 R2 deployed, Topology Builder will not allow you to define an instance of a Lync Server 2013 that is already in use in the topology.

Topology Builder will display the following message to inform you of this issue: "The SQL server [FQDN of the server] already contains a SQL instance hosting role 'User Store'."

http://technet.microsoft.com/en-us/library/gg425764.aspx

Guess a completely separate SQL server is the only way to go.