Usability concerns how easy the system is to operate, administer and maintain. Unlike reliability, availability and serviceability, usability is a fairly subjective issue. It does however present concrete design issues that can be analysed. The three basic issues are:

• The administrator is the focus of the usability of a system. It should be easy for them to use.
• Systems that are highly configurable are more usable than systems that do not offer configuration options. For instance, the installation of peripherals should be easy and chassis options should be flexible.
• Documentation and software add to the usability of a system.