Massively Distributed Database Systems Spring 2014 Ki-Joune Li Pusan 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 and Distributed 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. TransparencyDescription AccessHide differences in data representation and how a resource is accessed LocationHide where a resource is located MigrationHide that a resource may move to another location RelocationHide that a resource may be moved to another location while in use ReplicationHide that a resource may be shared by several competitive users ConcurrencyHide that a resource may be shared by several competitive users FailureHide the failure and recovery of a resource PersistenceHide 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 SystemDescriptionMain 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 applications. 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 distributed among four machines b)Situation after CPU 1 references page 10 c)Situation if page 10 is read only and replication is used

21 Comparison between Systems A comparison between multiprocessor operating systems, multicomputer operating systems, network operating systems, and middleware based distributed systems. Item Distributed OS Network OS Middleware-based OS Multiproc.Multicomp. Degree of transparencyVery HighHighLowHigh Same OS on all nodesYes No Number of copies of OS1NNN Basis for communication Shared memory MessagesFilesModel specific Resource management Global, central Global, distributed Per node ScalabilityNoModeratelyYesVaries OpennessClosed Open