The difference between cluster and distributed_PHP tutorial

The difference between cluster and distributed

The difference between cluster and distributed in web system.

Cluster:

A cluster is a group of service entities that work together to provide a service platform that is more scalable and available than a single service entity. From the client's perspective, a cluster looks like a service entity, but in fact a cluster consists of a set of service entities. Compared with a single service entity, a cluster provides the following two key features:

Scalability--The performance of the cluster is not limited to a single service entity. New service entities can be dynamically added to the cluster, thereby enhancing the performance of the cluster.

High availability - the cluster prevents clients from easily encountering out of service warnings through service entity redundancy. In a cluster, the same service can be provided by multiple service entities. If one service entity fails, another service entity will take over the failed service entity. The functionality provided by the cluster to recover from one failed service entity to another enhances application availability.

Distributed:

The so-called distributed computing is a computer science that studies how to divide a problem that requires a huge amount of computing power into many small parts, then allocate these parts to many computers for processing, and finally combine these calculation results to obtain The final result. Distributed network storage technology is to store data dispersedly on multiple independent machines and devices. The distributed network storage system adopts a scalable system structure, uses multiple storage servers to share the storage load, and uses location servers to locate storage information. This not only solves the bottleneck problem of a single storage server in traditional centralized storage systems, but also improves the reliability of the system. performance, availability and scalability.

Distribution refers to distributing different services in different places. Clustering refers to gathering several servers together to implement the same business.

Every node in the distribution can be clustered. And a cluster is not necessarily distributed.

For example: Take Sina.com. If there are more people visiting, it can be a cluster. A response server is placed in the front, and the following servers complete the same business. If there is a business access, the response server depends on which server. The load is not very heavy, whichever machine will be used to complete it.

Distributed, understood in a narrow sense, is similar to a cluster, but its organization is relatively loose. Unlike a cluster, it has an organizational structure. If one server collapses, other servers can pick up the slack.

Each distributed node completes different services. If a node collapses, the service will be inaccessible.

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