Server operating systems

The Microsoft Windows operating system is predominant among desktop computers, but in the world of servers, the most popular operating systems—such as FreeBSD, Solaris, and Linux—are derived from or similar to the UNIX operating system. UNIX was originally a minicomputer operating system, and as servers gradually replaced traditional minicomputers, UNIX was a logical and efficient choice of operating system for the servers. However, the market share of Windows server has been growing steadily, and has become the new top server operating system in revenue from sales, as of 2005.[1] However UNIX-based systems, many of which are free, are more popular.

Server-oriented operating systems tend to have certain features in common that make them more suitable for the server environment, such as the absence of a GUI (or an optional GUI); the ability to be reconfigured (in both hardware and software) to at least some extent without stopping the system; advanced backup facilities to permit online backups of critical data at regular and frequent intervals; facilities to enable the movement of data between different volumes or devices in such a way that is transparent to the end user; flexible and advanced networking capabilities; features (such as daemons in UNIX or services in Windows) that make unattended execution of programs more reliable; tight system security, with advanced user, resource, data, and memory protection, and so on. Server-oriented operating systems in many cases can interact with hardware sensors to detect conditions such as overheating, processor and disk failure, and either alert an operator, take remedial action, or both, depending on the configuration.

Because the requirements of servers are, in some cases, almost diametrically opposed to those of desktop computers, it is extremely difficult to design an operating system that handles both environments well; thus, operating systems that are well suited to the desktop may not be ideal for servers and vice versa. Nevertheless, certain versions of Windows are also used on a minority of servers as are recent versions of the popular Mac OS X (also Unix-based) family of desktop operating systems and even some proprietary mainframe operating systems (such as z/OS); but the dominant operating systems among servers continues to be UNIX versions or clones. Even in the case of Linux, configurations that are ideal for servers may be unsatisfactory for desktop use, and configurations that perform well on the desktop may leave much to be desired on servers.

The rise of the microprocessor-based server was facilitated by the development of several versions Unix to run on the Intel x86 microprocessor architecture. The Microsoft Windows family of operating systems also runs on Intel hardware, and versions beginning with Windows NT have incorporated features making them suitable for use on servers.

Whilst the role of server and desktop operating systems remains distinct, improvements in both hardware performance and reliability and operating system reliability have blurred the distinction between these two classes of system, which at one point remained largely separate in terms of code base, hardware and vendor providers. Today, many desktop and server operating systems share the same code base, and differ chiefly in terms of configuration. Furthermore, the rationalisation of many corporate applications towards web-based and middleware platforms has lessened the demand for specialist application servers.