Yet another vote for Debian. I find it works well with Xen virtualisation (with or without a chip with hardware virtualisation support, so pretty much any processor should do), giving you a stable OS that lets you install each of your important services (email, DHCP, DNS, etc) in a separate VM. Around 256MB per VM seems to be a practical minimum, so a server with a couple of GB of RAM in should let your run half-a-dozen or so small VMs.
Originally Posted by CHR1S
Linux's mdadm RAID is excellent and very flexible whilest also being recoverable - if your processor dies you can plonk the hardrives in a new box and boot using any boot CD with mdadm support and the RAID array should just automatically appear, ready to go - no rushing around trying to find a matching hardware RAID controller that understands the particular RAID metadata on your disks.
If you want a light-weight GUI to go on top of Debian, Xfce seems to be about the best I've found. No extanious bits and bobs all over the place - we're going to be using it at school for a ChromeOS-like OS that just loads up Firefox o startup and nothing else.
using ubuntu server 11 at home with mdadm for a mirrored 320GB array, after swearing at the disk manager once it was working it has been spot on.
found HOWTO: Linux Software Raid using mdadm - Ubuntu Forums helpful.
there was another guide as well but i cant find the link oops.
all running on a VIA C7 with a gig or so of ram, large data transfers see I/O CPU usage at around 50% (with just me using it)
found Webmin a nice tool for managing it all as well
do you require it to perfrom services such as dns,dhcp etc...?
if not = unraid else ubuntu server