Advanced operating systems
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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

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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


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