Raspberry Pi 3

Role: The Experimental Swarm

• Primary Role: K3s Kubernetes or Docker Swarm Cluster.
• Network: Plug these into a dedicated unmanaged switch like the D-Link DGS-105.

Architecture

Because older Pi 3 boards are frequently freed up as you upgrade to newer SBCs, they are perfect for grouping together into a sandbox environment.

Peripherals to Leverage

Buy a Multi-Port USB PD Charger (like a 6-port Anker) to power all of them cleanly from a single wall plug, eliminating power-brick clutter. Use this cluster to run low-stakes services like Uptime Kuma (to monitor the primary Observability Bastion) or Home Assistant tests without risking production data.