As I’ve stated in a previous post, I’m currently reading “Cloud Computing: Concepts, Technology & Architecture” by Thomas Erl. It’s a decent read, but one part had me puzzled in Sec. 5.4: Virtualization Technology:
Virtualization is the process of converting a physical IT resource into a virtual IT resource.
Most types of IT resources can be virtualized, including:
…
Power – A physical UPS and power distribution units can be abstracted into what are commonly referred to as virtual UPSs.
I’ve honestly never heard of a “Virtual UPS” before. I tried a bunch of a Google searches but to no avail. There’s nothing about such things in Amazon’s AWS docs, either, that I could find, or in its console for that matter. All I could find were red herring references to details things like a type of UPS that could make sure that your VMs were kept up and running. All in all, though, I don’t know why the author put this in there. Sadly, that was the most relevant search result. It’s certainly not common, as I found from several variants of Google searches to filter out everything related to the United Postal Service and Universal Power Supplies (you know, those adapters you use when you travel to Europe to charge your phone, not the Uninterruptable Power Supplies that ensure that momentary brownouts don’t take out your servers and the first desktop you assembled back in high school).
Anyways, the key premise of this brief post is that technologies such as Virtual UPSs really aren’t useful in the context of the cloud. You have a virtual host or a container; then it goes down. Such scenarios can happen because of your shitty code, the web server code, the virtualization software layer, itself, random transient errors, etc. Bottom line, who cares if you can spin up another instance that works. One of the big benefits of the cloud is that the cloud enables us to think about hosts as a commodity that can go down from transient issues intermittently but can be brought back up again quickly and automagically by provisioning a new instance. At such a layer of abstraction, low-level notions like a virtual uninterruptable power supply really don’t have any use or value in this new paradigm, because these lower level notions simply don’t have any meaning in the cloud.