You know the old saying in real estate, the most 3 important things in real estate are Location, Location, Location. Similarly in IT systems the 3 most important things are Boundaries, Boundaries, Boundaries.
Every boundary is an opportunity and not a good kind of opportunity.
This was brought home to me in Brian Krebs' recent post on Complexity as the Enemy of Security. Brian was discussing security and how complexity contributed to security exposures.
This maxim is true in many areas of IT. Recently I was discussing with a VP of a transportation firm on how to horizontally expand application servers for an existing application. He wanted to put an additional box in front of the application servers. I discouraged that because it added an additional boundary to the system. My suggestion was to do "outside in" routing at the remote clients and not introduce that additional boundary.
I used this methodology at a large forest products corporation to consolidate database and application server instances into a large server. While the instances still had their separate identities they were all contained in a single physical box. It made a tremendous improvement in availability.
I explored this phenomenon with the CFO relating how the old mainframe systems were easier to support because they used point-to-point circuits instead of TCP/IP networks. She hadn't considered this. It is incumbent on IT professionals to make sure that executives understand the downside of complexity.
At an international package delivery company we used this methodology to maintain extraordinary high availability. The mathematics of availability show that compounding 99% availability loses 1% for each additional boundary.
And boundaries aren't just physical. This maxim can be applied to changes in status of a system. Every time a system changes status there is an opportunity for it to fail. Simply put, if you don't reboot a server you won't suffer a restart problem.
While a single monolithic system won't meet today's demands, every boundary should be closely examined to determine if it can be eliminated.