Scale-up vs Scale-out Architecture, How is Your Organization Currently Scaling It's Storage Needs?

Traditionally, organizations world-wide have utilized Scale-up architecture when it comes to storage. What does this mean? Traditional scale-up architecture utilizes a dual-controller set-up, and adds storage drives as needed to increase storage capacity and performance. Run of storage, add another shelf. Seems pretty straight forward right? Run out of performance, not so straight forward...