Like desktop computers, servers can run a variety of operating systems, and systems specialists enjoy debating the relative merits of each. The most common are Unix (in its many flavors, most notably FreeBSD, Solaris, and Linux--which itself comes in many flavors), Microsoft's Windows Server System, and Apple's OS X Server. Unlike the world of desktop computers, where Microsoft dominates, among server operating systems, Unix traditionally has been the major player. In fact, Unix is most common operating system for web servers by a wide margin, although Microsoft recently been making gains.5.7
The choice of operating system is driven partly by the server hardware. Microsoft and Unix operating systems run on Intel-based processors (Unix can also run on several other classes of processor), and Apple's operating system runs on Apple servers.
The choice of operating system is usually transparent to the user of a server, and one should function as well as another. Some information technology departments, however, have rigid preferences for certain operating systems and hardware, and when planning a digital audio project, you might be expected to work with whatever server operating system happens to be supported. Smaller information technology departments, in particular, will be resistant to adopting a new server platform to support a single project.
This becomes an issue when planning a digital audio project, because the choice of operating system will, in turn, define the possible choices for the software that will drive the digital audio service.