ACM Computing Surveys (CSUR) - The MIT Press scientific computation series
On the criteria to be used in decomposing systems into modules
Communications of the ACM
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A distributed operating system provides the same functionality and interface as a monolithic operating system. That is, for both systems the goal is to make the computing and storage facilities as provided by the hardware available to the users of the system. In distributed operating system new hardware can be added to the system to increase the storage or computing power, or to increase the availability of the storage and computing services. During and after this addition, the interface to the system remains unchanged. Transparency of access is a key concept.The top-level interface consists of sophisticated command interpreters and editors, supported by a high-resolution graphical window system. This software is run by workstations. Workstations are powerful computer units, consisting of a CPU, memory, a bitmap display, keyboard, a pointing device such as a mouse, and a network interface. In addition, workstations are often equipped with a disk. The CPU is at least as powerful as those used in traditional computer systems, and the amount of memory is equivalent or even larger.A workstation is dedicated to one individual. Consequently, the workstation is idle most of the time. It is therefore tempting to use it as the main computing resource for the owner and perhaps others as well. It could also be used autonomously from the rest of the system in case of a failure. We are opposed to these uses of workstations, since we believe that workstations should only provide the top-level interface. In this paper we will outline our reasons for this, and show how this principle has been applied in the Amoeba distributed operating system.