massively distributed database systems spring 2014 ki-joune li lik pusan national university
TRANSCRIPT
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
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Distributed System - Scalibility and Heterogeneity
A distributed system organized as middleware. Heterogeneity and Scalibility
1.1
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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
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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
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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
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Software Concepts
• An overview of • DOS (Distributed Operating Systems)• NOS (Network Operating Systems)• Middleware
System Description Main Goal
DOSTightly-coupled operating system for multi-processors and homogeneous multicomputers
Hide and manage hardware resources
NOSLoosely-coupled operating system for heterogeneous multicomputers (LAN and WAN)
Offer local services to remote clients
MiddlewareAdditional layer on top of NOS implementing general-purpose services
Provide distribution transparency
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Network Operating System (1)• General structure of a network operating system.
1-19
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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
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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 applica-tions.
1.23
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Multitiered Architectures: Example
18
Alternatives of Multitiers Architectures
1-29
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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
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Comparison between SystemsA comparison between multiprocessor operating systems, multicomputer operating systems, network operating systems, and middleware based distributed systems.
Item
Distributed OS
Network OSMiddleware-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 communicationShared memory
Messages Files Model specific
Resource managementGlobal, central
Global, distributed
Per node Per node
Scalability No Moderately Yes Varies
Openness Closed Closed Open Open