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I’m thinking of experimenting with clustering RPis, but the thought of that mess of equipment (switch + multi-port USB charger) and cables is a bit of a turn-off.
Does anyone know if there are any limitations to running a cluster of Pis with power-over-ethernet? I’ve googled around but haven’t found any reference to anyone doing this before.
(I know you need the HAT to get PoE support, just wondering if there are any reasons it wouldn’t be viable.)
With a somewhat decent length ethernet cable, it is actually not too messy.
Depending on the power draw, you may want to make sure your switch also supports PoE+.
I have tested both PoE HATs and PoE USB Dongles on both RPi 3's and RPi 4B+'s and haven't had any issues. In that testing, however, I would caution against some of the PoE HATs that are made for RPi 4B+'s because some of them barely put out enough power and the one that did got quite hot.
In the end, in both the RPi 3 scenarios and the RPi 4 scenarios I ended up using the USB PoE splitter in conjunction with a PoE or PoE+ switch, run over a CAT 5e or CAT6.
In terms of quantity with which you can get away with... I can't speak to an upper limit really, as I was just fine running over 40 RPi's which used a handful of Unmanaged Switches.
In a couple instances during development and testing, I used Managed Switches just for the sake of organization. It starts to get a little tricky trying to track which port goes to which RPi...
