Operating System – Difference Between Distributed System and Parallel System

A distributed system is a model where distributed applications are running on multiple computers linked by a communications network. Sometimes it is also called loosely coupled systems because in which each processor has its own local memory and processing units. LOCUS and MICROS are some examples of distributed operating systems.

Parallel Systems are designed to speed up the execution of programs by dividing the programs into multiple fragments and processing these fragments at the same time. Flynn has classified computer systems into four types based on parallelism in the instructions and in the data streams. 

1. Single Instruction stream, single data stream
2. Single Instruction stream, multiple data stream
3. Multiple Instruction stream, single data stream
4. Multiple Instruction stream, multiple data stream

Advantages of Distributed Systems:

• Scalability: Distributed systems can be easily scaled by adding more computers to the network.
• Fault Tolerance: Distributed systems can recover from failures by redistributing work to other computers in the network.
• Geographical Distribution: Distributed systems can be geographically distributed, allowing for better performance and resilience.

Disadvantages of Distributed Systems:

• Complexity: Distributed systems are more complex to design and maintain compared to single computer systems.
• Communication Overhead: Communication between computers in a distributed system adds overhead and can impact performance.
• Security: Distributed systems are more vulnerable to security threats, as the communication between computers can be intercepted and compromised.

Advantages of Parallel Systems:

• High Performance: Parallel systems can execute computationally intensive tasks more quickly compared to single processor systems.
• Cost Effective: Parallel systems can be more cost-effective compared to distributed systems, as they do not require additional hardware for communication.

Disadvantages of Parallel Systems:

• Limited Scalability: Parallel systems have limited scalability as the number of processors or cores in a single computer is finite.
• Complexity: Parallel systems are more complex to program and debug compared to single processor systems.
• Synchronization Overhead: Synchronization between processors in a parallel system can add overhead and impact performance.
  

Difference Between Distributed System and Parallel System:

S. No	Parallel System	Distributed System
1.	Parallel systems are the systems that can process the data simultaneously, and increase the computational speed of a computer system.	In these systems, applications are running on multiple computers linked by communication lines.
2.	Parallel systems work with the simultaneous use of multiple computer resources which can include a single computer with multiple processors.	The distributed system consists of a number of computers that are connected and managed so that they share the job processing load among various computers distributed over the network.
3.	Tasks are performed with a more speedy process.	Tasks are performed with a less speedy process.
4.	These systems are multiprocessor systems.	In Distributed Systems, each processor has its own memory.
5.	It is also known as a tightly coupled system.	Distributed systems are also known as loosely coupled systems.
6.	These systems have close communication with more than one processor.	These systems communicate with one another through various communication lines, such as high-speed buses or telephone lines.
7.	These systems share a memory, clock, and peripheral devices	These systems do not share memory or clock in contrast to parallel systems.
8.	In this, all processors share a single master clock for synchronization.	In this there is no global clock in distributed computing, it uses various synchronization algorithms.
9.	E.g:- Hadoop, MapReduce, Apache Cassandra	E.g:- High-Performance Computing clusters, Beowulf clusters

A distributed system and a parallel system are two different types of computer systems, and the main difference between them is how they manage the processing and communication of tasks across multiple processors.

1. A distributed system is a computer system that consists of multiple interconnected computers or nodes, that work together to perform a task or a set of tasks. The processing is distributed across multiple nodes, and each node is responsible for performing a part of the task. In a distributed system, the nodes communicate with each other using a network, and the system is designed to handle data and tasks that are geographically distributed. Examples of distributed systems include the internet, cloud computing, and peer-to-peer networks.
2. On the other hand, a parallel system is a computer system that consists of multiple processors that work together to perform a task. In a parallel system, the processing is divided into multiple tasks, and each processor performs a separate task simultaneously. The processors communicate with each other using shared memory or message passing, and the system is designed to handle data and tasks that require high computational power. Examples of parallel systems include supercomputers and clusters.

In summary, the main difference between a distributed system and a parallel system is how they manage the processing and communication of tasks across multiple processors. In a distributed system, the processing is distributed across multiple nodes connected by a network, while in a parallel system, the processing is divided among multiple processors that work together on a single task.