The primary difference between a clustered system and a multiprocessor system lies in their physical structure and how they achieve parallelism: a clustered system uses multiple independent computers working together, while a multiprocessor system uses multiple CPUs within a single physical computer.
Clustered Systems
-
Definition: A clustered system consists of multiple independent and complete computers (nodes) that are interconnected and work together as a single, unified computing resource. Each node has its own operating system, memory, and I/O devices.
-
Characteristics:
- Loose Coupling: Nodes communicate via a network, often using message passing.
- Independent Nodes: Each node can function independently if the cluster fails.
- Scalability: Easy to add or remove nodes to increase or decrease computing power.
- High Availability: If one node fails, another can take over its workload.
- Cost-Effective: Can be built using commodity hardware.
-
Examples:
- High-Performance Computing (HPC) clusters: Used for scientific simulations, weather forecasting, and data analysis.
- Web server farms: Distribute web traffic across multiple servers.
- Database clusters: Provide redundancy and scalability for database applications.
Multiprocessor Systems
-
Definition: A multiprocessor system (also known as a symmetric multiprocessing or SMP system) contains two or more CPUs within a single physical computer. These CPUs share the same memory space and I/O devices.
-
Characteristics:
- Tight Coupling: CPUs share memory and communicate directly.
- Shared Resources: All CPUs have access to the same memory and I/O devices.
- Complex Architecture: Requires specialized hardware and operating system support to manage multiple CPUs.
- Higher Performance: Provides faster execution for parallel tasks.
- Single Point of Failure: If the system fails, all processing stops.
-
Examples:
- Desktop computers with multiple cores: Common in modern PCs and laptops.
- Server computers with multiple CPUs: Used for database servers, application servers, and other demanding workloads.
- Mainframe computers: Large, powerful computers used for critical applications.
Key Differences Summarized
| Feature | Clustered System | Multiprocessor System |
|---|---|---|
| Structure | Multiple independent computers | Single computer with multiple CPUs |
| Coupling | Loose (network communication) | Tight (shared memory) |
| Resource Sharing | Independent (own memory, OS) | Shared memory and I/O |
| Scalability | Highly scalable (add/remove nodes) | Limited by physical limitations of the motherboard |
| Availability | High (fault tolerance) | Lower (single point of failure) |
| Complexity | Complex software for managing the cluster | Complex hardware and OS for CPU management |
In essence, clustered systems achieve parallelism by distributing workloads across multiple independent machines connected via a network, while multiprocessor systems use multiple CPUs within a single machine to achieve parallelism.
