Determine services downtime by performing a test upgrade, probably by cloning the production environment on a virtualized system where you can perform snapshots and rollback with ease. Your clone must have the same/similar hardware specs to production.Take into account that some times, on big version upgrades, you may need to perform a 2-step upgrade, meaning that upgrading to the very latest version of a product some times is not possible, so you first attempt to upgrade to the first build of a...