SQL Server Patching a Mirror configuration

Hello,

We're planing to have two SQL servers updated by synchronous database mirroring. This will include a third environment configured as a witness server.

For standard windows patching - what order should we patch / reboot the servers?

From serverfault SuperCoolMoss

• The order would go like this:

  1. Update the secondary server (the one that is not currently serving connections)
  2. After it reboots, do a controlled mirroring failover to it
  3. Update the primary server (which at this point is no longer serving connections)
  4. After it reboots, you can do a controlled failover back to it if you want, but you don't have to. You can leave the connections running on the secondary box.
  SuperCoolMoss : Thanks Brent, how does patching the witness server fit in?

  Brent Ozar : If the witness server isn't involved in anything else whatsoever, then you can do that first. I usually see the witness being involved with other SQL Server activities, though - for example, it might be a mirroring partner for another primary server, so it can't be rebooted willy-nilly. If you're lucky enough to have a dedicated mirroring witness that does nothing else, then you can get it done first, but it doesn't matter whether it's first or last.

  Paul Randal : Be careful just leaving the connections running on the secondary box if you don't have a license for it. It's only free if you fail back to the original principal within 45 days.

  Brent Ozar : Great point, +1 on the comment. Didn't know about the 45-day limitation - I thought it'd be even shorter than that.

  SuperCoolMoss : Thanks Paul and Brent - Am I correct in thinking if all user databases are failed over to the secondary (no active connections to user databases on primary) then the 45 day limitation can be ignored?

  Paul Randal : No. The license you have is only for the principal instance - doesn't matter if nothing's using it.
  From Brent Ozar