I'm guessing you're asking this because you have a picture of a 'server' as a thing in a large rack? Nearly every tech business has a bunch of machines, everything from an old desk top to last year's laptop, which have been reinstalled with Linux or *BSD and are sitting on the network behaving, for all intents and purposes, as a 'server.' (they aren't moving or rebooting or having local sessions running on them, Etc).