I use Ubuntu for my file server. It's debian-based and has all the volume management stuff out of the box. I actually run it as a mythtv box as well, so it serves 3 purposes:

1) NFS and Samba fileserver
2) MPD (music player daemon) based jukebox
3) Mythtv video jukebox

I've been extremely happy running Ubuntu on it, and I've tried lots of different linux distros in my time.

-- Gary F.