mostly an excuse to play with virtualization, filesystems, and networking

No sorry, I meant which NAS are people using to run music servers like Blackcandy. I used to run a FreeNAS but need to upgrade badly.

I've been using TrueNAS for six years already. I've built a custom server

- Intel dual core Atom CPU

- Passive cooling for the CPU, two fans for the HDDs

- A small Supermicro motherboard with IPMI and six SATA connectors

- 16 gigabytes of ECC RAM

- Six 14 terabyte hard disks

- Fractal Design Node case

- ZFS with RAIDz2

But this setup is getting old, I've had a few errors already from the CPU. My plan next year is to build a rack server with a modern AMD Ryzen CPU, 64 GB of RAM, Proxmox with TrueNAS scale in a virtual machine and re-use the disks I have in the current setup.

Proxmox is much nicer for virtual machines and LXC, and if you need Docker, you can run them in the TrueNAS Scale VM.

Synology

2014 MacBook Pro in a cupboard with an external drive running Ubuntu. Integrated UPS!

Sounds like recipe for r/spicypillows

FreeBSD 14 on a mini-ITX supermicro mainboard and 5 drives in a Jonsbo NAS case.

Hardware wise I bought a TerraMaster F4-423 used last year for about 300€. It's a great device.

Software wise, I use Fedora Server, although if I had to reinstall now I would use AlmaLinux because I don't need the new stuff coming with Fedora Server on my NAS.

Dell R720XD

A custom built Debian machine with four HDDs in a ZFS volume backed up using restic