Today I have a server to repair or perhaps rebuild. It's an old HP ProLiant ML110 G4 that we bought new over a decade ago. It has a dual-core Intel Xeon processor and just 2G RAM but with NetBSD and Samba that's probably still adequate for a simple file server. I'm told it won't power up, so perhaps it just needs a new power supply. If the problem is more serious I'll have to find another server and reach for the backup tapes.
Recently I've considered OmniOS as a server operating system. Like NetBSD it's deliberately minimal. One possible advantage is its support for ZFS (yes, I know we'd need more RAM). Something that puts me off OmniOS though is an apparent lack of documentation. It seems to be built with the assumption that the server admin already knows Solaris or OpenSolaris and most of my SunOS experience dates back to when SunOS was a BSD.
There are some other alternatives to unix: I could try Linux or even Windows Server. I'll probably test these at home but NetBSD has been very stable for us so I'll stick with that for the production server. I'm a firm believer that "if it aint broke, don't fix it". The hardware's broken though, so let's hope I can fix that.