What Are You Made Of?
It is important to remember that a typical data center site is composed of many mechanical, electrical, fire protection, security, and other systems, each of which has additional subsystems and components. For a business-critical application, the facility should at least have an ability to control physical access. For example, in Oracle's primary data center located in Texas, the outer walls can withstand a semi-truck hitting the wall at 60 mph. While one hopes this never happens, it does provide a meaningful measure of protection against unwanted physical access to the building. In addition, embassy-grade baleens are raised and lowered to control vehicle entry. Full-time camera and armed guard surveillance monitors the approaches to the building, with physical access controlled by a combination of biometric devices and mantraps.
Physical security management is critical, but it's equally important for availability management to have high-quality power. At a minimum, the facility should be capable of operating for a fixed period of time when power is lost to allow for graceful shutdown. For mission-critical applications, the demands go further. A power outage in Memphis shouldn't affect users in Dallas or Los Angeles, much less in London, Tokyo, or Sydney.
A world-class data center has sufficient backup batteries and diesel fuel generators onsite to run uninterrupted for 72 hours. The facility would include measures to modify the site infrastructure activity without disrupting the computer hardware operation in any way. Such upgrades would include preventive and programmable maintenance, the repair and replacement of components, the addition or removal of capacity components, the testing of components and systems, and more.
As an example, for large sites using chilled water for cooling, this means two independent sets of pipes. Sufficient capacity and distribution must be available to simultaneously carry the load on one path while performing maintenance or testing on the other path. The physical infrastructure is important and forms the basis for high-quality management; many such facilities exist around the world today. A reliable and secure physical and networking infrastructure is a fundamental requirement for modern computing.