

One drive failure means an array is degraded until resilvering finishes (unless you have hot spare, at least then the array isn’t degraded and silvering a new drive isn’t as risky).
Resilvering is an intensive process that can push other drives to fail.
I have a ZFS system that takes the better part if a day (24 hours) to resilver a 4TB drive in an 8TB five-drive array (single parity) that’s about 70% full. When uts resilvering I have to be confident my other data stores don’t fail (I have the data locally on 2 other drives and a cloud backup).
I’d look at getting a used SFF (Small Form Factor) desktop for a LOT less than that Ugreen. I paid less than $50 for mine - at that price I can run a second one when I’m ready.
I’m currently running an old Dell SFF as my server, I’ve had Proxmox on it with 5 drives internally (2.5") with the OS on the NVME.
Initially it had 4GB of ram and ran Proxmox with ZFS just fine (and those drives were various ages and sizes).
It idles at 18w, not much more than the 12w my Pi Zero W idled at, but way more powerful and capable.