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Advanced Operating Systems. Welcome to this course, in Fall Semester 1389-90 Main TextBooks 1- Tanenbaum’s book 2- Chow’s Book 3- Singhal’s Book Other extra references: 1- Attieh’s book 2- Lynch’s book. Advanced Operating Systems. Assistants: to be announced. Evaluation:

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advanced operating systems
Advanced Operating Systems
  • Welcome to this course, in Fall Semester 1389-90
  • Main TextBooks

1- Tanenbaum’s book

2- Chow’s Book

3- Singhal’s Book

  • Other extra references:

1- Attieh’s book

2- Lynch’s book

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

advanced operating systems1
Advanced Operating Systems
  • Assistants: to be announced.
  • Evaluation:
    • Mid-Term Exam
    • Project
    • Review Paper
    • Final Exam
  • The course Home page and Mailing-list …
  • Office Hours: Sunday and Tuesday 8 - 9

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

1 introduction to distributed systems and distributed operating systems doss from tanenbaum s book

1Introduction to Distributed Systems and Distributed Operating Systems (DOSs)(From Tanenbaum’sBook)

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

definition of a distributed system 1
Definition of a Distributed System (1)

A distributed system is:

A collection of independent computers that appears to its users as a single coherent system.

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

definition of a distributed system 2
Definition of a Distributed System (2)

1.1

A distributed system organized as middleware.Note that the middleware layer extends over multiple machines.

goals in dss
Goals in DSs
  • Connecting Users and Resources
  • Transparency
  • Openness
  • Scalability

Will be discussed in the next slides.

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

transparency in distributed systems
Transparency in Distributed Systems

Different forms of transparency in a distributed system.

degree of transparency
Degree of Transparency
  • Is transparency good anytime and everywhere?
  • Tradeoff between transparency and performance.

- Updating a replicated database!

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

openness
Openness
  • Offering services based on standards.
  • Services are specified through interfaces, described in IDL (Interface Definition Language)
  • Interoperability: two implementations of a system to co-exist and work together; or

multiple systems developed by different vendors to be able to work with each other.

  • Portability: An application developed to work on A can be executed on another system B.
  • Separating policy from mechanism

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

scalability
Scalability
  • Definition of an scalable system?
  • 3 different dimensions
    • Size: Adding more users and resources to the system.
    • Geography: Users and resources can lie far apart.
    • Administration: Many administration organization!

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

scalability obstacles
Scalability Obstacles

Examples of scalability limitations.

scalability solutions
Scalability Solutions
  • Hiding communication latencies: try to avoid waiting for responses to remote service requests  Use Asynchronous Communication
    • Many applications cannot run on an asynch communication system
    • Next slide example.
  • Distribution: DNS as example
  • Replication: Caching and consistency!

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

scaling techniques 1
Scaling Techniques (1)

1.4

  • The difference between letting:
  • a server or
  • a client check forms as they are being filled
scaling techniques 2
Scaling Techniques (2)

1.5

An example of dividing the DNS name space into zones.

hardware concepts
Hardware Concepts

1.6

Different basic organizations and memories in distributed computer

systems

multiprocessors
Multiprocessors

A bus-based multiprocessor.

1.7

  • Memory is Coherent.
  • The bus is overloaded.
  • Caching: hit-rate?
  • Scalability?

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

software concepts
Software Concepts

An overview of

  • DOS (Distributed Operating Systems)
  • NOS (Network Operating Systems)
  • Middleware

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

uniprocessor operating systems
Uniprocessor Operating Systems

Separating applications from operating system code through

a microkernel.

1.11

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

multiprocessor operating systems 1
Multiprocessor Operating Systems (1)

A monitor to protect an integer against concurrent access.

monitor Counter {

private:

int count = 0;

public:

int value() { return count;}

void incr () { count = count + 1;}

void decr() { count = count – 1;}

}

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

multiprocessor operating systems 2
Multiprocessor Operating Systems (2)

A monitor to protect an integer against concurrent access, but

blocking a process.

monitor Counter {

private:

int count = 0;

int blocked_procs = 0;

condition unblocked;

public:

int value () { return count;}

void incr () {

if (blocked_procs == 0)

count = count + 1;

else

signal (unblocked);

}

void decr() {

if (count ==0) {

blocked_procs = blocked_procs + 1;

wait (unblocked);

blocked_procs = blocked_procs – 1;

}

else

count = count – 1;

}

}

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

multicomputer operating systems 1
Multicomputer Operating Systems (1)

General structure of a multicomputer operating system

Message Passing

1.14

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

distributed shared memory systems 1
Distributed Shared Memory Systems (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

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

dsm an interesting scenario
DSM – An Interesting Scenario!

False sharing of a page between two independent processes.

1.18

False Sharing!

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

network operating system 1
Network Operating System (1)

General structure of a network operating system.

1-19

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

network operating system 2
Network Operating System (2)

Two clients and a server in a network operating system.

1-20

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

network operating system 3
Network Operating System (3)

Different clients may mount the servers in different places.

1.21

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

positioning middleware
Positioning Middleware

General structure of a distributed system as middleware.

1-22

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

middleware and openness
Middleware and Openness

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.

1.23

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

comparison between systems
Comparison between Systems

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

clients and servers
Clients and Servers

General interaction between a client and a server.

1.25

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

an example client and server 1
An Example Client and Server (1)

The header.h file used by the client and server.

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

an example client and server 2
An Example Client and Server (2)

A sample server.

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

an example client and server 3
An Example Client and Server (3)

A client using the server to copy a file.

1-27 b

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

application layering processing level
Application Layering:Processing Level

The general organization of an Internet search engine into three different layers

1-28

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

multitiered architectures 1
Multitiered Architectures (1)

Alternative client-server organizations (a) – (e).

1-29

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

multitiered architectures 2
Multitiered Architectures (2)

An example of a server acting as a client.

1-30

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili

modern architectures
Modern Architectures

An example of horizontal distribution of a Web service.

1-31

OS2-Sharif University of Technology - Sem1-89-90; R. Jalili