1 / 16

Distributed Systems Architecture

Distributed Systems Architecture. Presenters Rose Kit & Turgut Tezir. Outline. Introduction to Distributed System Characteristics of Distributed System Advantages of Distributed System Disadvantages of Distributed System Loosely-coupled Systems Tightly-coupled system Array Processor.

arne
Download Presentation

Distributed Systems Architecture

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Distributed Systems Architecture Presenters Rose Kit & Turgut Tezir

  2. Outline • Introduction to Distributed System • Characteristics of Distributed System • Advantages of Distributed System • Disadvantages of Distributed System • Loosely-coupled Systems • Tightly-coupled system • Array Processor

  3. Introduction to Distributed System • Centralized System • A single computer with one ore more CPUs processes all incoming request • Problems with cost, reliability • Specification and implementation are defined within a single system • Distributed System • Opposite of centralized system • Set of separate computers that are capable of autonomous operation, link by a compute network. • Enable individual computers (different location) to share resources in the network • Server implementation for the same interface located in different servers.

  4. Distributed and Centralized Computer System

  5. Characteristics of Distributed System • Resource sharing • Resource provided by a computer which is a member of a distributed system can be shared by clients and other members of the system via a network. • “Resource Manager” is a software module (based on set of management policies) that provides interfaces which enables resource to be manipulated by clients, Openness • Openness • Resource sharing services can be incorporated without disruption or duplication of existing services • Concurrency • All concurrent access must be synchronised to avoid problems such as lost update, dirty read, incorrect summary & unrepeatable read.

  6. Characteristics of Distributed System • Scalability • flexible to grow in size. • Fault tolerance • the system appropriately handles errors • hardware redundancy, software recovery • Transparency • hide all unnecessary details from users • Example: Location transparency - clients do not need to know the location of the servers

  7. Advantages of Distributed System • Shareability • Allows systems to use each other’s resources • Expandability • Permits new systems to be added as members of the overall system • Local Autonomy • Manage local resources • Improved performance • Resource replication • Combined processing power of multiple computers provides much more processing power than a centralised system with multiple CPUs • Improved reliability and availability • disruption would not stop the whole system from providing its services as resources spread across multiple computers • Potential cost reductions

  8. Disadvantages of Distributed System • Network reliance • problems on network would disrupt activities in the system as a whole • Complexities • must be able to deal with errors from all computers that make up the distributed system • Security • private resources would be exposed to a wider range of potential hackers, with unauthorised accesses from any computers connected to the system • centralised system is more secure

  9. General Types of Distributed Systems • Loosely-Coupled Systems • Tightly-Coupled Systems • Array Processor Systems

  10. Loosely-coupled Systems • Loosely-coupled distributed systems are single-user computers or workstations that are locally networked enabling them to access shared data and resources located in other servercomputers • Most distributed systems links two types of computers, workstations and servers (also known as client/server). • An early example of the client/server model is the Xerox distributed system • Systems with different hardware and software can be networked together • Advantages of loosely coupled systems over tightly coupled systems: • More scalable. • Generally more reliable/fault-tolerant. • Allows sharing of widely separated resources.

  11. Loosely-coupled Systems

  12. A Loosely-coupled System Local Network Memory Memory Memory Memory Prg A Prg B Prg C Prg D Processor Processor Processor Processor I/O I/O I/O I/O

  13. Tightly-coupled system • Tightly-coupled system connects a number of processor into an integrated hardware system under the control of a single operating system. • The operating system assigns processor and memory space to users’ tasks and allow them to run at the same time. • The hardware environment includes a shared memory or a high-speed connection between several separate processor / memory systems with a unified virtual addressing system. This enables users’ tasks to communicate with each other and with the operating system. • Advantage of tightly coupled systems over loosely coupled systems: • Easier to program but expensive (Limited by the memory bandwidth)

  14. A Tightly-coupled Multiprocessor System Shared Memory Program A Program B Program C Program D Cache Memory Cache Memory Cache Memory Cache Memory Processor Processor Processor Processor Input / Output

  15. Array Processor • An array processor is similar to a personal computer with a large number of arithmetic and logic units linked in a regular array. They can be used to perform operations in parallel on arrays of data. • The distinguishing characteristics of such a machines is that the entire array of processors obeys a single stream of instructions, some of the instructions being applied to many data items distributed throughout the array of processing unit. • There are also other tightly–coupled distributed systems that are designed to make calculations faster by processing them in parallel. • Advantages: • Useful for achieving high processing speed when processing large regular set of data • Disadvantages • Geographical distribution • Many independent tasks need to executed at the same time.

  16. Array Processor M M M M M M M M M P P P P P P P P P Input / Output Program M: Memory P: Processor

More Related