Introduction

Readings

Van Steen and Tanenbaum: 5.1 Coulouris: 10.3

Definition

From the Tanenbaum and Steen textbook:A distributed system is a piece of software

that ensures thatA collection of independent computers that

appears to its users as a single coherent system.

Definition

Quote by Leslie Lamport:A distributed system is one in which I cannot get

something done because a machine I've never heard of is down.

Game Changer: 1980’s

Fundamental Shift

Gradually went from centralized systems to networked systems

The arrival of PCs and LANs led to applications that: Extracted information from central databases on

shared file servers Extracted information is integrated into

spreadsheets and other applications on the PC

Synchronized application updates were required

Tools needed to monitor and troubleshoot performance and other network problems

Emerging Characteristics

Multiple computers Concurrent execution Independent operation and failures

Communications Ability to communicate No tight synchronization

Relatively easy to expand or scale Synchronized application updates

Example (Coulouris)

the rest of

email server

Web server

Desktopcomputers

File server

router/firewall

print and other servers

other servers

print

Local areanetwork

email server

the Internet

intranet

ISP

desktop computer:

backbone

satellite link

server:

network link:

Example: A Typical Portion of the Internet (Coulouris)

Example: Portable and Handheld Devices in a

Distributed System (Coulouris)

Laptop

Mobile

PrinterCamera

Internet

Host intranet Home intranetWAP

Wireless LAN

phone

gateway

Host site

Evolution

In the 1990’s we saw the explosion of WWW

Companies began to use the web for information sharing and interactions with customers

Multi-tier applications emerged Customers connect (through a browser) to

many different applications Applications hosted on different servers

residing on different machines

Revolution:Cloud Computing

There is an emerging trend to move more and more computing functions into large shared data centers Amazon EC2 “hosts” data centers for

customers Google runs all sorts of office applications,

email, etc on their systems Yahoo! wants to be a one-source computing

solution IBM has a vision of computing “like electric

power”

Cloud Computing Concept

Google/IBM/Amazon/Yahoo! host the services

Email, file storage, IM, search

Databases, spreadsheets, office apps

Web services

Supporting Technologies

InfrastructureCore management and scheduling

functionsEvent notification servicesStorage systems (GFS)Monitoring, debugging, tuning

assistance We are increasingly seeing virtualization

becoming a part of this infrastructure

Supporting Technologies

Not just about hardware Software is needed to enable clouds:

Map-ReduceBigTableAstrolabeAmazon’s shopping cart

Course Topics

We have a limited time I would like to focus on the fundamental

concepts e.g., synchronization, replication, multicast

Provide some insight into how Amazon, Google work

Look at the hot topics through a critical analysis of papers

Undergrad vs Grad

This is an advanced graduate course Projects are not as well defined as found

in undergraduate courses You are expected to learn things outside

of the lectures More emphasis on reading research

papers More emphasis on presentations

Evaluation

Although I will present in the first part of this course I do expect 1 to 2 presentations from each student

You will be required to evaluate papers and provide brief reviews

There is one project

Reviews

Not all papers discussed in class will require a review

The goal of a review is to show that you have critically analyzed a paper

Reviews are one to two pages long

Presentations

Present a paper Each paper will have a presenter, advocate

and a devil’s advocate Present a technology

Examples: Amazon, eBay Can involve 2 to 3 people

Projects

Group based Creative Sufficiently challenging Types:

New idea Experiment with existing ideas Develop an application