What are clusters and LVS?

A cluster is a group of computers interconnected through a high-speed network and managed in a single system mode; many servers are brought together to provide the same service, and it appears to the client as if there is only one server . LVS (Linux Virtual Server) is a virtual server cluster system.

Cluster

• #A group of clusters interconnected by telling the network Computer group, and managed in a single system mode

• Combine many servers together to provide the same service, and it will appear to the client as if there is only one server.

• You can obtain relatively high gains in performance, reliability, and flexibility at a lower cost.

• Task scheduling is Core technology in cluster system

Cluster purpose

• Improve performance

  -such as computing intensive Type applications, such as: weather forecasting, nuclear test models

• Reduce costs

  -Compared to million-dollar supercomputers, the price is cheaper

• Improve scalability

  -Just add cluster nodes

• Enhance reliability

  -Multiple nodes complete the same function , to avoid single points of failure.

Cluster classification

• ##High-performance computing cluster HPC
  – Solve complex scientific problems with parallel applications developed in clusters.

• Load Balancing (LB) Cluster
  – Client load is distributed as much as possible between compute and cluster Evenly distributed.

• High Availability (HA) Cluster
  -Avoid single point of failure. When a system fails, fast migration is available.

LVS (Linux Virtual Server)

LVS is the abbreviation of Linux Virtual Server, which means Linux virtual server and is a virtual server cluster system. This project was established by Dr. Zhang Wensong in May 1998. It is one of the earliest free software projects in China.

LVS can be used to implement highly available and scalable network services such as Web, Mail, Cache and Media

The ultimate goal is to use the Linux operating system and LVS cluster software to achieve a highly available and high-performance , low-cost server application cluster.

LVS cluster composition

• Front-end: load balancing layer
  -consisting of a Or multiple load balancing schedulers constitute

• Middle: Server group layer
  -It is composed of a group of devices that actually run application services.

• Bottom: Data Sharing Storage Layer
  -Storage area that provides shared storage space

LVS terminology

• Directory Server: Scheduling Server
  -Server that distributes load to Real Server

• Real Server:Real Server
  -The server that actually provides application services

• VIP: virtual IP address
  -Publish the virtual IP address visited by users

• RIP: Real IP address
  -The IP address used on the cluster node

• DIP: The IP address of the node server where the scheduler connects.

  
  

##LVS working mode

VS/NAT

• -Virtual server implemented through network address translation

  -When there are large concurrent accesses, the performance of the scheduler becomes a bottleneck

VS/DR

• - Directly use routing technology to implement virtual servers

  -Node servers need to configure VIP, pay attention to MAC address broadcast

  -VS/TUN

  -Virtual servers are implemented through tunnels

Load balancing scheduling algorithm

LVS currently implements 10 scheduling algorithms

There are 4 commonly used scheduling algorithms

-Round Robin

-Weighted Round Robin

-Least Connections

-Weighted Least Connections )

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