The concept of dual-machine hot standby

The concept of dual-machine hot standby includes both broad and narrow sense.

In a broad sense, that is, for important services, use two of servers, backup each other, common execution of the same service. When a server fails, it can be serviced by another server, which automatically guarantees that the system will continue to provide services without the need for human intervention.

Two-machine hot standby solves the problem that the service is not interrupted when the primary server fails. However, in the actual application, there may be multiple servers, that is, server clusters.

Dual-Machine hot standby A shared storage device is generally required. In some cases, however, you can use two separate servers.

The realization of dual-machine hot standby, need to pass the professional cluster software or dual-computer software.

In a narrow sense, dual-machine hot standby is specifically based on Active/standby mode of server hot standby. Server data includes database data that is written to two or more servers, or uses a shared storage device. Only one server runs at the same time. When one of the servers running fails to boot, the other backup server activates the standby machine via software diagnostics (usually through a heartbeat) to ensure that the application is fully restored in a short period of time. (Related articles: double-standby, dual-machine and dual-machine duplex the difference).

We can look at the typical mode of dual-machine hot standby through a typical dual-machine hot-standby software PCL ha:

-active/active mode

-active/standby mode

In fact, dual-machine hot standby may be extended to a multiple-machine cluster: Multi-machine cluster mode

Dual-machine hot standby is generally used to have a database or other data applications. The application servers (or other services that do not write data) should be grouped in the field of load balancing before data.