Lync 2013 has a lot of new(ish) features. To me, the interesting ones are on the backend support, how HA is accomplished, server pairing, and things like that. Recently, I had to chase down the specifics of the new backend SQL support and how it fits into the new architecture.
To that end, I submit the following bullets regarding Lync 2013 and the SQL support.
- Each pool member has a local SQL Express running.
- Each pool member synchronizes with other pool members.
- One pool member is active for the backup service and synchronizes with the active pool member in the paired pool.
- Each pool member synchronizes with the backend full SQL also.
- The full SQL does NOT synchronize with the paired pool full SQL.
- If your paired pool (Pool A) contains the Central Management Store (CMS), then when you pair Pool A with Pool B, Pool B will have a backup copy of the CMS. Only one of these CMS copies is "master" at any one time. If you need to failover Pool A to Pool B, then you need to move the CMS master to Pool B using the invoke-csmanagementserverfailover cmdlet. For more information see this link.
- Each full SQL for each pool can also provide an archiving, monitoring, and Persistent Chat database.
- Persistent Chat uses Log Shipping to and stretches its’ pool across sites to provide for resiliency.
- Paired pools are also backup registrars for each other (not really a SQL thing, but an interesting point before you go pairing pools).
But each full SQL could fail, leaving those services unavailable.
- To answer this HA requirement, Lync 2013 can use SQL mirror to provide for intrasite High Availability - not to be confused with the ability of the paired pool to assume full services if needed.
Clear as mud?