In writing about Performance and Scalability I referenced a quote that I have provided in a number of presentations regarding a valuable interaction with a client. All software architects and managers need to clearly understand this for their own sites in order to enable technical resources to deliver a highly scalable solution.

Development Manager:  We need a maintenance window for software upgrades and new releases.
CTO:  No Downtime.
Development Manager: But we need this to fix problems and improve performance.
CTO:  No Downtime.
Consultant (aka Ronald Bradford):  Mr CTO. What is your definition of no downtime?
CTO:  We serve pages, we serve ads.
Consultant: We can do that.

Asking the right question about the uptime requirements completely changed the architecture needed to meeting these specific high availability needs.

It is important to know with this major TV network client the answer was not updating content, selling merchandise or enabling customers to comment. Each of these needs requires a different approach to high availability.