Distributed Operating System - Distributed Operating Systems - Lecture Slides, Slides of Computer Science

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Amoeba Distributed Operating

System

What is Amoeba?

• Amoeba is a distributed operating system

• Runs on a simple micro-kernel

• Developed by Andrew Tanenbaum

• Has user transparency

• The user logs into the system not a specific

machine

• When a program is initiated the system decides

what machine will run it.

Goals of Amoeba

• There are four main goals

• Distribution
  • Connecting together many machines
• Parallelism
  • Allowing individual jobs to use multiple CPUs easily
• Transparency
  • Having the collection of computer act like a single system
• Performance
  • Achieving all of the above in an efficient manner

Key Concepts

• Micro-kernel
  • A simple micro-kernel is the basis for Amoeba
  • All computers in the network run this kernel
  • It handles the memory management, I/O, communication, object primitive, and basic processes
• Remote Procedure Calls (RPC)
  • Used for communication between client and server
  • Accessed by stubs which are created by Amoeba Interface Language

• Objects
  • The abstract data type used by Amoeba
  • Can be either software or hardware
    • But software is more common
  • Each object has a list of operations that can be preformed and a capability
• Capability
  • 128 bit value
  • Used to verify that the user has permission to access the object
  • Capabilities are encrypted

• Bullet Server
  • Store files in a contiguously fashion
  • Most files can be sent in a single RPC
  • Designed to be a dedicated server
• Directory Server
  • Handles naming of files
  • Knows the physical location of each file

Architecture

Significant Points

• The system is free
• It has not had an official update in over 10 years
• Can use older/slower CPUs to create a powerful system
• Micro-Kernel allows for other file systems to be created
• Has four main goals
  • Distribution
  • Parallelism
  • Transparency
  • Performance
• Has many UNIX like commands and programs
• Can only hold programs as large as its physical memory