Massively Distributed Database Systems

Spring 2014Ki-Joune Li

http://isel.cs.pusan.ac.kr/~likPusan National University

An assignment- Choose an electronic (or electric) device - Define additional functions with

. data storage

. communication (infrastructure or ad-hoc)

. some computation

. and others Do not mind how difficult it would be to implement.

- Example

Massively Distributed Databases vs. Distributed Databases

This lecture includes

• Distributed Systems and Database Systems• Overview• Synchronization• Consistency and Replications

• P2P• Ad-Hoc Network and MANET• Data on Air• Cloud• RESTful• Ubiquitous Computing and IoT

5

Definition of a Distributed System

• Distributed system : 1) A collection of (scalability)2) independent computers that (heterogeneity)3) appears to its users as a single coherent system

(transparency)

• Distributed System versus Parallel System• Separated Operating System vs. Single Operating System• Message Passing vs. Shared Memory

Distributed Systems andDistributed Database Systems- Overview

7

Why Distributed System ?

• Performance• Incremental Growth (Scalability)

• 1 single mainframe of price W• N small machines of price W/N

• Fault Tolerance• 1 single mainframe : critical weak point• Failure of a machine : replacement by other machines

• Geographical Distribution and Availbility• Flexible configuration

• e.g. 1 Disk server, 3 Computing servers, 1 Graphic server, etc.• Geographical availibility

8

Distributed System - Scalibility and Heterogeneity

A distributed system organized as middleware. Heterogeneity and Scalibility

1.1

9

Distributed System - Transparency

Different forms of transparency in a distributed system.

Transparency Description

Access Hide differences in data representation and how a resource is accessed

Location Hide where a resource is located

Migration Hide that a resource may move to another location

Relocation Hide that a resource may be moved to another location while in use

Replication Hide that a resource may be shared by several competitive users

Concurrency Hide that a resource may be shared by several competitive users

Failure Hide the failure and recovery of a resource

Persistence Hide whether a (software) resource is in memory or on disk

10

Distributed System : Heterogeneity

Server A

Driver for A Driver for B

Server B Server C

Driver for C

Application Program or Client

Client has to be provided with one different driver for each server

11

Distributed System : Heterogeneity and Object-Oriented Approach

Server A Server B Server C

Application Program or Client

Wrapping with predefined interface

Predefined interface

Encapsulation : Object-Oriented Approach

12

Software Concepts

• An overview of • DOS (Distributed Operating Systems)• NOS (Network Operating Systems)• Middleware

System Description Main Goal

DOS Tightly-coupled operating system for multi-processors and homogeneous multicomputers

Hide and manage hardware resources

NOS Loosely-coupled operating system for heterogeneous multicomputers (LAN and WAN)

Offer local services to remote clients

Middleware Additional layer on top of NOS implementing general-purpose services

Provide distribution transparency

13

Network Operating System (1)• General structure of a network operating system.

1-19

14

Network Operating System• Two clients and a server in a network operating system.

1-20

15

Middleware• General structure of a distributed system as middleware.

1-22

16

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 appli-cations.

1.23

17

Multitiered Architectures: Example

18

Alternatives of Multitiers Architectures

1-29

19

Multicomputer Operating Systems• General structure of a multicomputer operating system

1.14

20

Distributed Shared Memory Systems

a) Pages of address space distrib-uted among four machines

b) Situation after CPU 1 refer-ences page 10

c) Situation if page 10 is read only and replication is used

21

Comparison between SystemsA comparison between multiprocessor operating systems, multicomputer operating systems, network operating systems, and middleware based distributed systems.

ItemDistributed OS

Network OS Middleware-based OS

Multiproc. Multicomp.

Degree of transparency Very High High Low High

Same OS on all nodes Yes Yes No No

Number of copies of OS 1 N N N

Basis for communication Shared memory Messages Files Model specific

Resource management Global, central

Global, distributed Per node Per node

Scalability No Moderately Yes Varies

Openness Closed Closed Open Open