Simple understanding of HA and ha cluster removal

hain highly available clusters,English is all called high availability, in a nutshell, a cluster is a group of computers that provide users with a set of network resources as a whole. These individual computer systems are the nodes of the cluster.

The advent of high-availability clusters is to make the overall service of the cluster as usable as possible, thus reducing the loss caused by the computer hardware and software errors. If a node fails, his backup node will take over his responsibilities in a matter of seconds, so the cluster will never stop for the user.

The main function of high-availability cluster software is to realize the automation of fault checking and business switching. Only two nodes of the high-availability cluster become dual-machine hot standby, using two servers to backup each other. When one server fails, it can be serviced by another server, thus realizing that the system can provide services without the need of manual intervention. Dual-Machine hot standby is only a high-availability cluster, the high-availability cluster system can support more than two nodes, provide more than the dual-machine hot standby, higher functionality, to meet the changing needs of users.

three ways to implement HA :

(1) Master-Slave

Under normal circumstances, the work is undertaken by the primary node, only when the primary node fails, the server will automatically switch to the slave node, the node will start the service, usually do not start the service, the primary server must have a cluster IP(vip), Services, Public storage. Once the primary server fails, the three will automatically switch to the slave node.

The node is used only if it fails, so it is more wasteful.

(2) Symmetrical type

This approach typically consists of 2 nodes and one or more services, for two different servers, no absolute master, and no absolute from.

Two nodes detect each other's state, and when a node fails, the service on that node switches to another IA node. This will ensure that the service is running properly.

(3) Cluster Type

This approach typically consists of multiple nodes and multiple services, each of which might or may not run, and each server monitors several specified services, and when one of the nodes fails, it automatically switches to a node in the set of servers.

Then the HA cluster is built, this article mainly introduces the removal of the cluster

1. Stop related services

clusvcadm-d httpd # # # stop service

2. If you have a mount, you must first uninstall the appropriate Mount

3. Delete

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(1) such as: Select all nodes, click Leave Cluster, the following interface appears

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(2) then select the node and Click Delete to remove

Here the delete action mainly completes two parts:

A. To delete a master configuration file /etc/cluster/cluster.conf

B. close the appropriate startup item Cman ramanager CLVMD modclusterd

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Only Modclusterd in these startup items need to be manually shut down and stop the boot entry

4. Storage Exit

the host of the Ricci node needs to exit

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Simple understanding of HA and ha cluster removal