Mike Kavis explains that in today’s environment, even a short amount of downtime can result in lost revenue or customers which can be detrimental to a business. He discusses methods for ensuring satisfactory performance while system upgrades are being made:
Continuous operations manages software and hardware changes in a way that is non-disruptive to the end users. Even though software and servers may be taken offline during planned maintenance, it is performed in a way where customers continue to be serviced by the previous versions of the application and are eventually switched over to the newer version once it has been deployed and successfully smoke tested.
Check out the full post, Continuous Operations for Zero Downtime Deployments, from The Virtualization Practice.