An overview of the Amoeba distributed operating system

Lecture Notes in Computer Science, 1990

Centre for Mathematics and Computer Science Amsterdam AMOEBA is a research project to build a true distributed operating system using the object model. Under the COST11-ter MANDIS project this work was extended to cover wide-area networks. Besides describing the system, this paper discusses the successive versions in the implementation of its model, and why the changes were made. Its purpose is to prevent ourselves and others from making the same mistakes again, and to illustrate how a distributed operating system grows in sophistication and size. I. Why This Paper "Those who learn nothing fi'om history are doomed to repeat it"-Santayana For about eight years now, we have been doing research on distributed operating systems, not only behind our desks, but also behind our terminals. The distributed system we are developing is called AMOEBA[l], and it is constantly evolving. It is being developed at the Vrije Universiteit and the Centre for Mathematics and Computer Science (CWI), both in Amsterdam. AMOEBA currently runs on Motorola 68020, National Semiconductor 32032, and MicroVax II processors. Both Ethemet and the Pronet token ring are supported by AMOEBA, and can be connected by a bridge. COST11-ter MANDIS is an international project investigating the management requirements for large international networks of computers. It has adopted the object-model as a framework within which to discuss the management of wide-area distributed systems. To experiment with this, the MANDIS project adopted the Amoeba distributed operating system, extended with a gateway for wide-area communication. Amoeba systems in Holland (Vrije Universiteit, CWI), the U.K. (Harwell Laboratories, Haffield Polytechnic), in Berlin (GMD/FOKUS) and in Norway (University of Troms0) have been connected into a single, transparent distributed system.

UNIX has been around now for almost 20 years. At the time UNIX began, most departments felt themselves well-endowed indeed if they owned a single PDP-11/45 with 256K memory and a 2.5M RK05 disk. Nowadays a laptop would be embarrassed to have only that. It is our hypothesis that UNIX is no longer the appropriate kind of operating system for the 1990s. In this paper, a new system, Amoeba, will be described, that we believe meets the requirements for distributed computing in the 1990s.

ACM Computing Surveys, 1985

Distributed operating systems have many aspects in common with centralized ones, but they also differ in certain ways. This paper is intended as an introduction to distributed operating systems, and especially to current university research about them. After a discussion of what constitutes a distributed operating system and how it is distinguished from a computer network, various key design issues are discussed. Then several examples of current research projects are examined in some detail, namely, the Cambridge Distributed Computing System, Amoeba, V, and Eden.

1991

This paper compares two distributed operating systems, Amoeba and Sprite. Although the systems share many goals, they diverged on two philosophical grounds: whether to emphasize a distributed computing model or traditional UNIX-style applications, and whether to use a workstation-centered model of computation or a combination of terminals and a shared processor pool. Many of the most prominent features of the systems (both positive and negative) follow from the philosophical differences. For example, Amoeba provides a high-performance user-level IPC mechanism, while Sprite's RPC mechanism is only available for kernel use; Sprite's file access performance benefits from client-level caching, while Amoeba This work was supported in part by the Netherlands Organization for Scientific Research (N.W.O.) under grant NF 62-334.

The current direction of computer systems is increasingly moving away from centralised system and moving towards distributed sets of workstations and personal computers connected by a network, known as distributed systems. This has led to the development of specialised operating systems to take full advantage of the resource sharing potential that a distributed system provides. The specialised operating systems being developed for these situations are known as Distributed Operating Systems. Research into this area is still at the primary stage with little firm evidence indicating what components of Distributed Operating systems are more important than others.

The VAMNET is a hybrid operating system environment for distributed applications in a heterogeneous environment, concerning both the hardware architectures used and operating systems already present, for example the UNIX−OS. The VAMNET consists of several parts. Some of them can operate standalone. All of them build up a hybrid distributed operating system environment with some new features never seen before. These parts are:

1979

Roscoe is an operating system implemented at the University of Wisconsin that allows a network of microcomputers to cooperate to provide a general-purpose computing facility. After presenting an overview of the structure of Roscoe, this paper reports on experience with Roscoe and presents several problems currently being investigated by the Roscoe project.

Distributed Systems Engineering, 1993

Unlike many other operating systems, Amoeba is a distributed operating system that provides group communication (i.e., one-to-many communication). We will discuss design issues for group communication, Amoeba's group system calls, and the protocols to implement group communication. To demonstrate that group communication is a useful abstraction, we will describe a design and implementation of a fault-tolerant directory service. We discuss two versions of the directory service: one with Non-Volatile RAM (NVRAM) and one without NVRAM. We will give performance figures for both implementations.

Microprocessing and Microprogramming, 1988

A new generation of operating system was born during the last ten years: a distributed operating system oriented network. Three key-concepts are strongly developed: standardization, distribution and parallelism. One of these systems is CHORUS TM. This project launched at INRIA has elaborated an architecture for distributed systems. CHORUS is now being commercialized by the CHORUS systems company; it will be ported in the next few years on different machines, starting with the sPs7, PC/AT and SUN. CHORUS offers UNIX TM compatibility, is independent of the hardware architecture and of the network.

1993

Building the hardware for a high-performance distributed computer system is a lot easier than building its software. In this paper we describe a model for programming distributed systems based on abstract data types that can be replicated on all machines that need them. Read operations are done locally, without requiring network traffic. Writes can be done using a reliable broadcast algorithm if the hardware supports broadcasting; otherwise, a point-to-point protocol is used. We have built such a system based on the Amoeba microkernel, and implemented a language, Orca, on top of it. For Orca applications that have a high ratio of reads to writes, we have measured good speedups on a system with 16 processors.