I'm using Debian GNU/Linux on one primary storage server (hexacore
AMD Phenom II, 16GB memory) which
exports disks: 16TB on
ZFS via Samba, NFS, iSCSI, AirVideoServer, AFP and DAAP.
A firewall, running from a USB
stick uses a heavily modified Debian Live with a dual 1Tb
network card for broadband and internal network connection.
The firewall is also responsible for internal NTP, DHCP and DNS
services, to simplify setting up a new machine.
Another server (AMD Athlon II, 8GB memory)
hosts all my virtual machines, running directly from
iSCSI on VirtualBox.
There is currently about 11 virtual machines running all
the time, most of them on Debian GNU/Linux,
used for development, testing, VoIP switching
User authentication and authorization is done using OpenLDAP and MIT
Kerberos V across the network.
All machines are headless, but a VNC server is running on the storage
just in case.
I chose Debian GNU/Linux because of simplicity and extensive software
repository. You just can't beat over 6000 packages available! No matter the
need, chances of it being packaged and ready to run, after a simple
apt-get install package, is huge.