We're planning on purchasing a new server and consolidating most of our websites onto it. The initial thought was to use Windows Server 2012 with 4 VMs on it (1 e-commerce web, 1 e-commerce database, 1 non-commerce web, 1 non-commerce database).
However, one of the things that has always bothered me is the downtime when installing software and OS updates. How would I accomplish high availability during software/OS updates? Can you do it with 1 server, or does it require 2 servers due to host server updates? Is Network Attached Storage a prerequisite to get this working properly?
New to virtualization, so links to good resources are appreciated.