We have OS patches scheduled for cms and the www servers this Thursday morning, starting at 9:30 am. Here's the schedule:
9:30 - Authoring and Replication are suspended on cms. Patches are applied on cms, and the server is rebooted. This process should take less than 10 minutes. Authoring will be re-enabled after that (9:40 or so).
9:45 - 10:30 - OS patches are applied on each of the three www servers. Replication will be offline while this is going on, but external access to the www servers will not be interrupted.
10:30 - (or sooner, if the patches on www are complete) - Replication will be back on its regular schedule.