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Introduction Chapter 1 Part II Hardware and Software Concepts Hardware Concepts (1) A DS = machines connected together How are these machines connected together? Review: multiple-CPU computer Characterization Hardware Concepts (2) 1.6

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introduction

Introduction

Chapter 1

Part II

Hardware and Software Concepts

hardware concepts 1
Hardware Concepts (1)
  • A DS = machines connected together
  • How are these machines connected together?
  • Review: multiple-CPU computer Characterization
hardware concepts 2
Hardware Concepts (2)

1.6

Different basic organizations and memories in distributed computer systems

multiprocessors 1
Multiprocessors (1)

Single

Address

Space

Similar

CPUs

Direct, uniform

Access to memory

A bus-based multiprocessor

1.7

  • Traffic Problems
  • Caching (hit ratio, consistency)
  • Scalable?
multiprocessors 2
Multiprocessors (2)

1.8

  • A crossbar switch
  • An omega switching network
multicomputers
Multicomputers
  • Each node is an autonomous machine
    • Private memory
  • Lower traffic than multiprocessors
    • CPU-CPU versus CPU-Memory traffic
  • Homogeneous or Heterogeneous
homogeneous multicomputers 1
Homogeneous Multicomputers (1)
  • Similar nodes
    • Same processors and memory space
  • Homogeneous access to network
    • Single network
  • Bus-based or point-to-point communication
heterogeneous multicomputers
Heterogeneous Multicomputers
  • Different nodes
    • Nodes can be complex systems
  • Non-homogeneous access to network
    • Different networks
  • DS are commonly built on this hardware category
    • Need software to make it transparent
software concepts
Software Concepts
  • A DS is similar to an OS
    • Resource management
    • Virtual machine
  • OS =
    • Tightly coupled
    • Loosely coupled
uniprocessor operating systems
Uniprocessor Operating Systems

1.11

  • Separating applications from operating system code through a microkernel.
multiple cpu operating systems
Multiple CPU Operating Systems
  • An overview between
  • DOS (Distributed Operating Systems)
  • NOS (Network Operating Systems)
  • Middleware
multiprocessor os 1
Multiprocessor OS (1)
  • Similar to uniprocessor
  • Single ready queue
  • Mutual exclusion through monitors and semaphores
  • Multiple CPUs
multiprocessor dos 1
Multiprocessor DOS (1)

Ready queue

Single Ready Queue

multiprocessor dos 2
Multiprocessor DOS (2)

CPU

CPU

CPU

Kernel

multiprocessor dos 3
Multiprocessor DOS (3)
  • A blocks or time-quantum expires
  • CPU 1 runs the scheduler and chooses D

A (W|R)

A (X)

  • Schedule A again on which CPU??

B (X)

C (X)

D (X)

D (R)

E (R)

C

B

D

A

OS

java monitors 1
Java Monitors (1)

public class Counter {

private int count = 0;

public synchronized void reset() { count = 0;}

public synchronized int value() { return count;}

public synchronized void inc() { count = count + 1;}

public synchronized void dec() { count = count – 1;}

}

  • A monitor to protect an integer against concurrent access.
java monitors 2
Java Monitors (2)

Java Compiler

Lock object

Counter

Object

public synchronized void reset() { count = 0;}

public synchronized void reset() {

acquire(this.lock);

count = 0;

release(this.lock)

}

multicomputer dos 1
Multicomputer DOS (1)

1.14

  • General structure of a multicomputer operating system
multicomputer dos 2
Multicomputer DOS (2)

1.15

  • Alternatives for blocking and buffering in message passing.
multicomputer dos 3
Multicomputer DOS (3)
  • Relation between blocking, buffering, and reliable communications.
distributed shared memory
Distributed-Shared Memory
  • Multicomputers are harder to program
  • Multiprocessors are easier to program
  • Multicomputers are more efficient and better scalable than multiprocessors
  • DSM offers a reconciliation
page based dsm example 1
Page-Based DSM Example (1)
  • Pages of address space distributed among four machines
  • Situation after CPU 1 references page 10
  • Situation if page 10 is read only and replication is used
page based dsm example 2
Page-Based DSM Example (2)

X

Y

1.18

  • False sharing of a page between two independent processes.
network os 1
Network OS (1)
  • Hardware is not homogeneous
  • More primitive than DS
    • Not fully transparent
network os 2
Network OS (2)

1-19

  • General structure of a network operating system.
network os 3
Network OS (3)
  • Services:
    • rlogin
    • File transfer
  • This led to the client/server organization
network os 4
Network OS (4)

1-20

  • Two clients and a server in a network operating system.
network os 5
Network OS (5)

1.21

  • Different clients may mount the servers in different places.
dos and nos versus ds 1
DOS and NOS versus DS (1)
  • DOS qualifies as DS?
    • Computers are not independent
    • Easy to use and transparent
  • NOS qualifies as DS?
    • No single coherent view
    • Scalable and open
positioning middleware
Positioning Middleware

1-22

  • General structure of a distributed system as middleware.
middleware
Middleware
  • Local system provides:
    • Local resource management
    • Communication mechanism
  • Middleware does not manage the local nodes
  • Middleware hides heterogeneity
    • Should not call local services directly
middleware types
Middleware Types
  • File-based (NOS + Transparency)
    • For traditional files only
  • RPC-based
    • Hides communication
  • Object-based
    • Remote Method Invocation
  • Document-based
    • The Web
middleware services
Middleware Services
  • Communication Facilities
  • Naming
  • Persistence
  • Distributed Transactions
  • Security
middleware and openness
Middleware and Openness

1.23

  • In an open middleware-based distributed system, the protocols used by each middleware layer should be the same, as well as the interfaces they offer to applications.
comparison between systems
Comparison between Systems

Very High

High

Low

High

No

Yes

No

Yes

N

N

1

N

Shared

memory

Messages

Files

Model specific

Global,

distributed

Per node

Global,

Central

Per node

Yes

Varies

Moderately

No

Closed

Closed

Open

Open

  • A comparison between multiprocessor operating systems, multicomputer operating systems, network operating systems, and middleware based distributed systems.
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