The term “server” does not make a clear distinction between software and hardware. It often refers to computers on which services are made available. However, multiple software servers, such as mail servers, application servers or web servers, can be easily installed on one single server computer or server system. Server hardware is characterised by special features. These may include a large internal memory, large hard disk space, powerful CPUs or high I/O throughput and high reliability. In most cases, systems run 24/7.