Lync Server 2013 now supports using SQL clustering for the SQL store. From the Database Software Support TechNet article:
Lync Server 2013 supports the use of either SQL mirroring or SQL clustering for each Lync Server database. You can easily set up SQL mirroring with the Topology Builder tool in Lync Server 2013. For SQL failover clustering, you must use SQL Server for setup.Lync Server 2013 supports SQL clustering topologies for all deployments, including greenfield deployments and organizations that have upgraded from previous versions of Lync Server.SQL Clustering support is for an active/passive configuration. For performance reasons, the passive node should not be shared by any other SQL instance.The following support is included:
Can we expect to support "always availibility groups" technology introduced by SQL 2102, and which seems to be the future for the high availibility ?
This technology is a mixed of mirroring and clustering !
Is there a projected date for its support (or never supported) ?
Currently SQL "always on" is not supported. I don't have any information on if/when the support statement might change.
So I wonder if this also means if you are using clustering, that you can do a Lync metropolitan pool design (stretched pool between 2 low-latency locations), which prior to this was no longer supported (in favor of the new pool pairing option).
No, the Metropolitan Site Resiliency design is not supported in Lync Server 2013.
In a paired pool scenario, will the fail-over function be automatic with a cluster?
In a paired pool scenario you will need to run the PowerShell cmdlets for failover, no matter if you're using SQL clustering or SQL mirroring.
What is the difference between SQL "always on" and SQL Active/Passive clustering?
Hopefully this helps to explain some of the differences:
Do we required SQL clustering while installing Enterprise Server Setup
SQL clustering isn't a requirement, but is highly recommended if you aren't going to deploy SQL mirroring and want high availability for the SQL backend.