How we view a data center has changed with the introduction of new technologies and software development methods. We will begin with a recap of the characteristics of a fully self-managed data center and go on to explain how our views have changed over time:

It's worth noting that, in all the examples in this book, there is still an underlying data center that has to be managed, but now we're talking about shifting that responsibility of management. In the preceding diagram, each stream of evolution is not tightly linked. For example, monoliths can still be run on private or public clouds. In this section, we will cover the evolution of hardware over time and focus in on the following topics:

• The physical data center
• Colocating our gear
• Cloud born

Your typical data center consists of a room with some metal racks arranged into rows with corridors between the rows. Each rack is filled with servers, networking gear, and maybe storage. The room must be kept at a consistent temperature and humidity to maintain the efficiency and reliability of the hardware components within the servers and other pieces of kit. The machines and equipment in the room also need power to run—lots of power.

Often three phases of power are needed to power back up batteries (in an uninterruptible power supply) in case of a brief power interruption, and then one or more backup power generators are used in the event of sustained mains power loss.

All of these components that make up a data center require special technical engineers to install and maintain them. All of these components also have dependencies for installing the application that runs the business code.

Once the servers are racked and plumbed into power and networking, you still need to install and configure them, as well as the operating system and the latest patches. The administration and maintenance of these things doesn't stop once the application is deployed either, so this would require dedicated operations staff.

Wouldn't it be good if we didn't have to be concerned about challenges such as finding available thermal space or adding redundant power sources? The drive to gain efficiencies in the way we do business has led to the emergence of new models, such as the next one.

Thankfully, if we already have our own servers that we need to run, we can use what's called a colocated space. This is when an organization running a data center has spare space (space meaning rack space, thermal space, power space, and networking space) and will rent it to you for a fee. You still maintain total control over your own server hardware.

The good thing about renting space in a data center is that we can reduce the number of specialist engineers that are needed to manage the hosting. We still need hardware and storage engineers, but we don't have to worry about making sure the air conditioning is operational, keeping track of the leasing and maintenance contracts, or depreciating the non-server assets over a given period of time.

Colocating can also go a step further where, instead of providing your own servers, you can rent the actual bare metal as well. This can save the burden on the finance team that's related to tracking IT assets.

Most consumers of server resources are not in the business of building data centers and aren't looking to scale the business or create this capability. They are concerned about building their application into a product that has business value. This group of builders needs a system that abstracts the details of the physical hardware and insulates the consumer from the failure of that hardware. They can't wait around to procure more hardware to scale if their product suddenly becomes popular.

A lot of these drivers (and there are plenty of others) are the reason that the cloud as we know it today was conceptualized.