What is the relationship between hot standby and cluster and load balancing?

Only one host is working, so the load cannot be shared equally. Only one machine is working at a time. If the work machine fails, all services will be transferred to another machine through the cluster. The transmission time varies from 30 seconds to 2 minutes, depending on the amount of data.

Most of them are used in environments with high security requirements and no 24-hour staff on duty.

Load balancing:

When two or more machines are running at the same time, there is no distinction between primary and secondary, which requires load balancing equipment and data synchronization software, and basically only the equipment that receives requests at the front end is used. When a single device fails, all application requests are shared equally by other devices.

Most of them are used in places with very large traffic. As long as one device is working, access will not be interrupted.

The difference between hot standby and load balancing is that:

1, dual-machine hot standby is equivalent to two servers, one of which is the standby of the other, and can also be the standby of each other; When the host runs the service, the standby machine is in the detection state. After the host fails, the standby machine will take over the service of the host.

2. Load balancing is to add a load balancing server to these two servers (or more than N servers), and the role of the load balancing server is to evenly distribute the user's requests to all nodes; Improve the processing capacity of the whole cluster; Realize the balance of network access.

3. Dual-machine hot standby is a product to ensure 24*7 hours high availability and non-stop, while load balancing is a product designed to solve the problem of excessive server pressure and a large number of concurrent network requests.

4. The advantages of dual-machine hot standby are: uninterrupted user service; Advantages of load balancing: WEB access is smooth, and user requests are evenly distributed on all nodes.

5. Disadvantages of dual-machine hot standby: adding an array to increase storage space in the traditional way also forms a single point of failure; Dual-machine hot standby may become virtual, because once the array crashes, the service also means stopping. If possible, it is a good idea to synchronize data with software instead of array, and array is used as the storage of backup data. )

6. Disadvantages of load balancing: Static WEB is applicable. Not if it's a database. At present, there is no complete solution to the multidirectional synchronization of the database (for example, a user is assigned to the server 1, and he adds a message to the database; When he visits server 2 next time, his original database information will not exist.

For the dynamic and frequently updated WEB, multi-directional data synchronization is also difficult, but now I have a good solution, because the load balancing server is added, so that each node is redundant; But the load balancer will form a new single point of failure, so if you want to add load balancing equipment, you must choose two redundant equalizers.