How are you defining a site and uptime? Are you talking about dynamically switching systems to allow for upgrades without downtime? I'm mostly wondering how i

How are you defining a site and uptime? Are you talking about dynamically switching systems to allow for upgrades without downtime? I'm mostly wondering how it compares with the setup at my current location. I have worked on systems that were designed for this, but I'm not sure if it's cost effective for most web applications. Most things can wait on occasion. Thank you.