Combining HA and DR

Question

The best guidance I've found is this, though I'm having difficulty understanding some aspects of it. A summary of the advice is to create farms such as:

farm 1:

• Availability Group 1 with Config database on SQL1 and SQL2, in sync mode
• Availability Group 2 with content database on SQL2 in Async mode (syncing with sql3 in farm2)

farm 2 (DR farm)

• Availability Group 3 with Config database on SQL3 and SQL4, in sync mode
• Availability Group 2 with content database on SQL3 in Async mode

In the above, a failure in SQL2 will require a failover to Farm2, as SQL1 has no access to the content db.

Do I understand correctly that I need to tell my DBAs the following:

• Keep SQL2 (with the content dbs) as the active node
• Never simply failover to SQL1, as users will lose access to all content (patching SQL2 will require a failover to the DR farm, for example)
• Restore the search config database to the dr farm any time the search config changes, then recreate the search service and do a full crawl

This also means that when I configure SharePoint:

1. Provide the listener name for the system databases (this allows SP to keep functioning when sql fails over)
2. Provide the alias of SQL2 for the content databases (this allows me to switch the server for the content dbs)

Any thoughts on this?

Answer 1

Your Content and most Service Application databases should be in Sync mode between SQL1 and 2. This will give you an 'any time failover' option, including during business hours. The only database you should not have in Sync mode is the Usage database (this database can be unavailable). For the Usage service, point at a specific database.

Your Prod -> DR via ASync is correct -- and do not sync Usage.

For Search, I would instead just plan on manually keeping the Search schema in sync. Easier to deal with, in my opinion.

For SharePoint, during install, yes use the AG Listener name! SQL Alias should not be used in an AOAG configuration. This applies to all Service Applications (sans Usage) and Content Databases created.