Originally posted by: statik213
anybody here work for blizzard?
Doubt it.
But running on anything but clusters of relatively lightweight machines wouldn't make much sense.
I do know what Battle.net runs on, since it's hosted at the same colocation provider we use for one of our sites at work.
Actually, they occupy 3-4 racks right beside us

All are Compaq ProLiant DL360's(1U 2-way capable boxes), and they seem to be running some homebrewn OS, most likely a Linux distro tailored to their needs.
And no I haven't/couldn't looked at any prompts to see this, but they do leave their installation discs plainly visible
The WoW realms are probably some similar setup, a custom installation disc that adds whatever software they use for their realms to a very basic clustered Linux system.
How many boxes make up a realm is anyone's guess, but probably quite a few.