I'm wondering whether several Raspberry Pi Zeros, connected through Ethernet hardware on their GPIO pins, could be used as a small k3s cluster. Since k3s already puts noticeable pressure on a 1 GB Raspberry Pi 3, I'm skeptical that a Pi Zero with 512 MB of RAM could run it at all. Would a Pi Zero have any realistic chance of working as part of the cluster, perhaps alongside a more powerful Raspberry Pi?
3 Answers
Clustering does not make several Pi Zeros behave like one larger computer with no manager. Distributed systems divide work among independent machines, and something still has to coordinate scheduling, service discovery, or job distribution. You can build a useful cluster for learning or parallel workloads, but ordinary programs will not automatically combine all the Zero CPUs and RAM into one unified system.
A Pi Zero is not a realistic choice for the k3s control plane because it falls below the documented memory requirements. However, it may be able to run as an agent or worker, especially if the control plane is hosted on a Raspberry Pi 4 or 5. The practical value would be limited, though, since each Zero adds very little computing power and still requires networking, storage, and management.
There are cluster-oriented hardware projects that connect multiple Pi Zeros and provide a way to provision them as separate nodes. Depending on the hardware, they may communicate over USB networking rather than ordinary Ethernet. Each Zero would still be an independent computer, not part of one shared-memory machine.
Could the Zeros be networked through the expansion board over USB? I’m not sure whether that setup provides normal network interfaces or just a way to manage the boards.
So I could use my existing Pi 4 for the control plane and connect several Pi Zeros as workers. It sounds possible, although mostly as a learning project rather than an efficient setup.