A small home lab, three years in
It started as one small machine running a file server and a build runner. It is now three machines, one switch, and a power bill I no longer look at directly. Here is what survived contact with reality.
What stayed
The small always-on box. Four cores, 16 GB, two SSDs in a mirror, 27 W at idle. It runs the boring things: DNS, backups, a couple of containers that should never be important enough to page anyone. Three years, one fan replacement.
The cheap managed switch. I bought it to learn VLANs and stayed because it has never dropped a link.
What went back
The big tower. It was fast, it was loud, and it ran for perhaps forty hours in a year. Everything I actually needed from it fits on the small box; everything else runs in CI for a few dollars a month.
The Raspberry Pi cluster. Four boards, four power supplies, four SD cards that failed in sequence. It taught me a lot about distributed failure modes and nothing about anything I needed.
The purchase that mattered
A decent UPS. Not for outages, which are rare here, but for the two-second brownouts that were quietly corrupting filesystems twice a year. The cheapest reliability work I have ever done.
Most home lab advice is about capacity. Almost all of my problems were about power and time.