[YorickPeterse]

For Linux this will vary between distributions and configurations. For example, based on some testing I did today using mkosi [1] (for reasons unrelated to this discussion), a bare-bones Fedora 43 installation uses about 130 MiB of RAM, while a Debian installation uses a little more than 100 MiB.

IIRC last time I tried a bare-bones FreeBSD installation it used about the same amount of memory, maybe a little more based on how ZFS is set up.

[1]: https://github.com/systemd/mkosi

[tiltowait]

ZFS will happilly (and intentionally) gobble up available RAM for ARC. On my 64GB system, ARC is using 42.4GB, but this memory is quickly reclaimable if it's needed. That said, I had very bad experiences trying to run ZFS on an underprovisioned system.