----------
What can I do with Turing Pi?
Home server (homelab) and cloud apps hosting
Learn Kubernetes, Docker Swarm, Serverless, Microservices on bare metal
Cloud-native apps testing environment
Learn concepts of distributed Machine Learning apps
Prototype and learn cluster applications, parallel computing, and distributed computing concepts
Host K8S, K3S, Minecraft, Plex, Owncloud, Nextcloud, Seafile, Minio, Tensorflow
What people use it for? Mostly to learn how to deal with problems that arise from managing a cluster and running software on it. Can you build a website that tolerates getting one of the nodes or hard drives turned off?
Some people use such solutions for productive things, like a Home Server, but a store-bought NAS or a single PC is usually more performant. A PI cluster might be less power hungry in some scenarios.
Some people use them as build/test platforms for code that should run on ARM architectures. Others have used them to host a website from their internet connection (I know...).
Some people just have fun tinkering with such things....
4 seems like a very useless number to me. 4 raspis is more expensive and less useful than a used dual xeon on ebay. I could imagine maybe there's a use for something with 16 slots? or at least 8? But I don't get these cluster boards (or, for that matter, storage enclosures!) which presume I can do something fundamentally different with 4 small computes than 1.
You can always connect 2 or 4 of these together.
But I understand what you mean. A project I want to build one day, when I have the time and learn ethernet interfacing through PCB's is to build a single board cluster of Octavo SoM modules. They are individually inexpensive and it'd be relatively easy to build a board with a dozen of them connected to a switch chip.
Spinning up VMs is sort of fine, but they don't have quite the performance or management characteristics of a real cluster. The network is slow, the nodes individually are not very powerful, you have to work out how to image each physical machine, nodes break or have I/O errors, ...
Basically everything here can be done on a single multicore computer (which is already a distributed system in many respects):
https://turingpi.com/12-amazing-raspberry-pi-cluster-use-cas...