If you have a HA system you should run reports against the standby server not the active one.
From what I have been told by Cisco CUIC does this automatically.
If you are not using CUIC there are a couple of ways to determine which server is active/standby.
If you don't have a HA system then you would need to run out of hours
This information came from Cisco Partner presentations I have never seen a Cisco public document.
Graham