We have two windows sql server 2008 R2 instances with mirroring configured. We want to upgrade them to SQL server 2014R2. How will this up gradation effect the mirroring between the servers, and also how should I proceed with this upgrade without causing an outage. As per my research I can upgrade the mirrored server first to 2014 and then do a failover on 2008 server to make it mirror and the 2014 as principal and follow the same procedure to upgrade 2008 as well. Could some one please shed more light to it. What are some intrinsic points that I need to take care of?