An Overview of the Amoeba Distributed Operating System

1
An Overview of the Amoeba Distributed Operating
System

• Mallikarjuna Reddy Srinivas Vadlamani
• University of California
• Irvine

2
Outline

• Introduction
• What is Amoeba?
• Design goals
• Architecture
• Communication primitives
• Resource management
• Priority Mechanism
• Summary
• Acknowledgements

3
Motivation for Distributed Systems

• Fall in microprocessor prices during early 80s
• Mainframes set-up expensive
• Search for efficient and economical substitutes
• Goals
• Distributed Resource Management
• High Availability
• Simplicity
• Parallelism
• Transparency
• scalability
• fast file system

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Design Goals of Amoeba

• Distribution connecting together many machines
• Transparency collection of computers acting
  like a single system
• Parallelism allowing individual jobs to use
  multiple CPUs
• Example the traveling salesman problem
• Fault Tolerance
• Boot Service
• Performance achieving all of the above in an
  efficient manner

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Architecture

• Workstations
• Used by users to access the system
• Limited processing power but not dumb
• Pool Processors
• Heavy duty computation
• Dynamically allocated to user tasks
• Can be multicomputers or multiprocessors
• Specialized Servers
• Example File or Directory servers
• Gateway
• Connects Amoeba to a WAN
• Converts data between FLIP and TCP/IP

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Architecture contd...

WAN
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Communication Primitives

• Remote procedure call based
• FLIP protocol for communication Fast Local
  Internet Protocol
• Advantage increased performance over TCP/IP
• Disadvantage need a gateway to connect the LAN
  to a WAN
• Amoeba Interface Language (AIL)
• Generates stubs
• Handles marshalling/unmarshalling of parameters
• Preserves transparency of the system

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Resource Management

• Computation done by processor pools
• Resource Manager on each node
• Tracks and controls resources on its node
• Dedicated Process Server
• Tracks which processors are free
• Allocates tasks to a group of processors
• Preserves transparency
• Allocation process is unknown to the user
• User has no control over allocation

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Priority Mechanism

• A Bank Server
• Analogy with a monetary bank
• Regulates access to shared resources
• Example of a shared resource is processing power
  of CPUs
• On initiation each process gets some number of
  tokens
• Can be thought of as virtual money held by the
  process
• To gain access to shared resources, process has
  to expend money
• At any given moment, the richest process gets
  access to the shared resource

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Summary

• Architectural Features
• Transparent distributed computing using a large
  number of processors
• Support for parallel computing
• Micro-kernel architecture
• High performance communication using RPC and FLIP
• Weaknesses
• Not compatible with UNIX
• Virtual memory not supported (for performance
  reasons)
• Performs poorly when there is insufficient memory
• No NFS support

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Acknowledgements

• Andrew S. Tanenbaum et al
• The Amoeba Distributed Operating System A
  Status Report
• Apan Qasem, CS Dept, Florida State University
• An Introduction to the Amoeba Distributed
  Operating System
• Yasir Ali
• An Overview of the Amoeba Distributed Operating
  System
• Kingsley Cheung, Gernot Heiser, School of
  Computer Science and Engineering, University of
  NSW, Sydney, Australia
• A Resource Management Framework for
  Priority-Based Physical Memory Allocation