The last five decades of computing have seen a gradual progression of architectural abstraction layers. Around 50 years ago, IBM mainframes gained virtualization capabilities. Despite explosive progress in the sophistication of hardware following Moore’s Law, there wasn’t too much further innovation in abstraction layers in server computing until well after the dawn of the microcomputer era, in the early 2000s, when virtualization suddenly became all the rage again. (I heard a rumour that this was due to certain IBM patents expiring, but maybe that’s an urban myth.) Different types of hypervisors emerged, including early forms of containers.

Then we started to realise that a hypervisor wasn’t enough, and we needed a whole management layer to keep control of the new “VM sprawl” problem which had arisen. A whole bunch of solutions appeared, including the concept of “cloud”, but many were proprietary, and so after a few years OpenStack came along to the rescue!

But then we realised that managing OpenStack itself was a pain, and someone had the idea that rather than building a separate management layer for managing OpenStack, we could just use OpenStack to manage itself! And so OpenStack on OpenStack, or Triple-O as it’s now known, was born.

Within and alongside OpenStack, several other new exciting trends emerged: Software-Defined Networking (SDN), Software-Defined Storage (e.g. Ceph), etc. So the umbrella term Software-Defined Infrastructure was coined to refer to this group of abstraction layers.

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