Is it possible to mirror SQL Server 2008 and SQL Server 2008R2 databases?

Question

Just curious whether it's possible to mirror databases across versions.

Answer 1

Yes and no.

Yes, it is possible to establish a mirroring session between 2008 and R2, as long as the R2 acts as a mirror. But as soon as a failover occurs and R2 becomes the principal, the R2 will upgrade the database to version 661 (the R2 database version). Since 2008 only understands version 655, it will no longer be possible to ever bring that database back online on the 2008 server.

Mirroring between different versions is often used to upgrade servers with minimal impact on production.