Does VCS require "shared disks"?

No, VCS does not require that your nodes are connected to shared disks. However, most people like to have storage that can be deported and imported during failover. If your applications do not need this, then you do not need shared storage. The VCS installation and setup will not ask if you have shared storage. This is great for people who don't have the shared storage ready, but still want to try out or test VCS.