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Distributed Systems

• Distributed systems are a type of computer system design composed of multiple interconnected devices or nodes linked via a network.
• Tasks and responsibilities are distributed among these connected devices.
• They work together as a single integrated system.
• A distributed system is a software system in which different components reside on multiple, physically separate computers connected across a network.
• These components interact and coordinate their activities through message passing.

Distributed Systems and Parallel Processing

• Key concepts include: Cloud Computing, Virtualization, Clustering, Distributed System Models, Cloud Programming, Service Oriented Architecture, Grid Computing, and Peer-to-Peer Computing.

Distributed System (Introduction)

• Distributed systems are designed to be highly efficient and use resources from multiple interconnected devices.
• They are characterized by significant advantages including load balancing, fault tolerance, scalability, and resource utilization.

Distributed Systems Definition

• Distributed systems consist of multiple independent computers connected via a computer network.
• These computers collaborate to achieve a common goal.
• These computers appear to act as a unified system.
• Data and task management are distributed across multiple connected machines.

Advantages of Distributed Systems

• Load balance and redundancy: Distributing work across multiple computers can manage and maintain a balance in the system. This improves performance and response time.
• Fault tolerance: If one computer fails, the other computers in the system can continue to function and provide services, significantly increasing the system's stability and flexibility.
• Scalability: Adding more computers to a distributed system easily expands capacity and resources. This enables the system to grow and handle increased workloads without disrupting service.
• Use of distributed resources: Distributed systems can utilize various resources including memory, processing units, and distributed databases which allows for better performance of applications and processing of large datasets.

Key Aspects of Distributed Systems

• Independent computers
• Unified system (Middleware)

Middleware

• Middleware software works between two or more programs to translate information between them or connect them.
• It resides between application software and the operating system or network operating system, or database management system.
• Middleware acts as an intermediary layer to facilitate communication and interaction between applications and other components in the system.

Middleware Functions

• Session Management
• Security
• Data Transformation
• Error Handling
• Communication
• Service Administration

Distributed System Architecture

• Layers of functionality are designed to enhance how the parts of a system interact and communicate to achieve a common goal, improving overall performance and preventing bottlenecks.
• This architecture allows for scalability and flexibility in accommodating multiple interconnected devices.
• The distributed system architecture is based on several layers, each with a specific function, such as data management, communication, and application layers. The network layer connects the different hardware elements.

Distributed System Characteristics

• Transparency
• Flexibility
• Reliability
• Performance
• Scalability
• Heterogeneity
• Security
• Failure handling
• Openness
• Concurrency
• Consistency
• Resource Sharing

Transparency

• Hiding details (location, structure, and functioning of system components) for user
• Making it seem as if the system is one singular unit
• User awareness of the dispersed nature of the system is not needed for proper functioning.
• The system must be able to handle the interaction between software and hardware components, ensuring it can handle failure from any part without complete system shutdown.

Distributed Systems Applications

• Social networks
• High-traffic websites
• Online banking systems (e-banking)
• Online gaming platforms
• Distributed Databases and Data Warehouses
• Distributed Information Systems
• Collaborative Design and Modeling Applications

Distributed Computing System

• Independent computers are connected to a shared network to provide a shared computing environment.
• Multiple computers collaborate similarly to one big computer.

Scalability

• The ability of a system to handle more user access and more data as the system expands.

Heterogeneity

• The ability of a system to work with a variety of software and hardware components, without problems with integration.

Failure Handling

• A system's ability to keep working even if there are partial failures of devices or software.

Other aspects of Distributed Systems

• Load Balancing: Distributing tasks fairly to different resources.
• Rollback/Recovery: Saving checkpoints/snapshots to easily return if errors occur.
• Distributed Database: A database where data resides on dispersed computers across a network.

Distributed Computing system

• Multiple computers interconnected to achieve common goals through network.
• Each connected computer serves as both client and server, distributing tasks and providing data over the network.

Distributed Database Systems

• Distributed databases are comprised of databases distributed over different locations on a network.
• They combine database management systems with computer network technologies.
• Systems aim to control data access through a central system.

Distributed Pervasive Systems

• Distributed pervasive systems involve networked resources and services accessible across different devices and locations .
• These resources offer a range of integrated computing services including storage, processing, and messaging capabilities, often operating independently while presenting a unified view to users.
• The user experience is simplified and they don't need to oversee the multiple locations where the resources exist.

Cloud Computing Principle

• Cloud computing focuses on accessing applications, data storage, and services through the internet, rather than requiring a dedicated system or device.
• The concept emphasizes the separation between user and resource, in contrast to running everything locally or via a dedicated server.

Client/Server Model

• This model involves a client (user) and server (computer), where requests are sent and responses are delivered.
• This model defines how an application is structured, which includes a distinct front-end interface for the user (client) and a back-end for data processing and storage (server).
• Separate parts of a task are performed on separate computers
  • Requests from the user trigger specific tasks on the server.

Distributed Object Model

• It treats all devices interconnected in the network alike allowing them to function as clients and servers simultaneously.

Software Architecture (Different Models)

• Client/Server Model: The client sends requests to the server. The server responds. Data/result exchange occurs through a network.
• Distributed Object Model: This model assumes that all devices/computers are peers. They interact via a request/response architecture.

Application Layer

• This layer encompasses user interfaces that present data to the end user.
• This layer handles the program logic and processes required to present the data appropriately.

Client-Server Architecture Variations

• Two-tier: Primarily focuses on the client and the server.
• Three-tier: Enhances functionality by introducing an intermediate layer between client and server.

Distributed Operating System (DOS)

• A system that provides a unified view to users, while underlying elements are distributed and independent.
• Multiprocessor OS: Manages multiple processors within a single computer.
• Multicomputer OS: Manages resources from multiple computers interconnected in a network.

Network Operating System (NOS)

• A system intended to operate across a network, enabling computers to share resources and communicate.
• It's designed to handle heterogeneity and does not present a fully integrated view to users.