Mainframe to Cloud – a short history

To understand Cloud technologies we need to understand the older technologies. Cloud is often considered an evolution of existing technologies rather than a brand new technology and start building software in a cloud-first view, rather than how it compares to older technologies. But, as the cloud evolved from older architectures the comparison will always remain.

So a short history lesson:

In the beginning was the mainframe, a single large computing hub, with terminals (screen and keyboard) that were distributed where people sat and did their work. While it looked like people were doing work at a computer at their desk the computer was actually in the computer room and they were working on what was termed a dumb terminal as it had no processing capability of its own.

Then came personal computers which moved the processing to the desktop. Personal computers were often linked to a bigger computer in the backend but had processing capabilities of their own, CPU, memory, and storage. The personal computer originally had all the programs installed as applications on the device. These programs would then make network calls to a database sitting somewhere else that would answer queries that the application would display to the user. This was called client-server (client = desktop, server = database)

Client-server then evolved into a three-tier technology. Some of the processing that the desktop was doing was moved to a server, so the client application started displaying information to the user instead of processing the data, processing (and database access) was handled by the server layer. If this sounds similar to the web, in a way it was, but instead of using a browser you would have had a custom-built interface doing the display.

But, the internet and browsers were the next progression, where instead of installing a client on your machine you could just access the application through a web browser. Originally the web browser would access business applications installed on a web server within the companies own data center (the same data center where the mainframe used to live). The database was also hosted within the data center, so everything was on-premise managed by the companies own IT staff.

Now this is where the cloud comes in ????

Cloud providers started making the servers available in their own data centers and allowed other companies to buy access to the servers. The servers remained in the cloud providers’ ownership and companies rented them. The original servers were just the same as the servers that IT was installing in the data center so this was Infrastructure as a Service (IaaS).

But many companies did not want to worry about the installation of server software on the IaaS servers they were renting so the Cloud providers started doing the installation themselves and sold access to the software level for hosting applications rather than to the whole server, in other words, they started selling the platform for applications (PaaS).

Big software companies were still selling software to companies who were then installing the software either on-premise or at the cloud data center. But this still required the company to have its own IT team who understood the software. So many big software companies started selling the installation services as part of their offering so in fact, the customer was only buying the software pre-installed somewhere in the world (SaaS).

PaaS still linked the software developers were making to a specific platform. So, cloud providers started allowing the upload of just source code that could be run when required. These functions were therefore independent of a specific platform people had to rent and would run and be charged for only when used (Faas). The advent of FaaS has also started the term of ServerLess computing. ServerLess is the ability to write and deploy code without ever having to worry about the Infrastructure or Platform the application is running on. This allows developers to write code and load it to the cloud and the whole system works without anyone knowing where it is actually installed.

Cloud providers have now started making many other platforms available to companies. For example, containers can be run on the cloud, or machine learning training can be done in the cloud. Each of these becomes a new service and could be abbreviated to <X>aaS e.g. A.I.aaS or Containers as a service.

Cloud providers are continually adding new services. We have already run out of <X> letters for services and only a few are ‘official’ abbreviations anyway. As the cloud expands we will be provided with new services all the time, as IT professionals we need to be aware of as many services as possible, though it will be impossible to know them all.