Glossary: Application hot standby, cold standby

In computer server backup and recovery, a cold server is a backup server that is used in the event that the primary server is lost. Cold backup servers are basically only powered on with the software installed and configured, then powered off until needed.

A warm server is generally powered on periodically, updated according to the contents of the primary server, and then powered off. Warm backup servers are often used for replication and mirroring operations.

The hot backup server (hot server) is always on and keeps synchronization with the host. When the host fails, the hot backup server can be enabled at any time to replace it.

As part of the Software Assurance Agreement program, Microsoft currently offers a free software agreement for cold backup servers used for disaster recovery, but not for warm and hot backup servers.

Dual-system hot standby is the so-called active/standby mode. Server data, including database data, is written to two or more servers at the same time, or a shared storage device is used. When the active server fails , the standby machine is automatically activated through software diagnosis (usually through heartbeat diagnosis) to ensure that the application can be fully restored to normal use within a short period of time.

Dual-machine mutual backup , on the basis of dual-machine hot backup, two relatively independent applications run on two machines at the same time, but both are set as backup machines. When one server fails, the other server can be The application of the failed server is taken over in a short time, thus ensuring the continuity of the application. This method is actually an application of dual-machine hot backup. It avoids the use of four servers for two applications to implement dual-system hot backup respectively.

duplex , two or more servers are active, running the same application at the same time, to ensure the overall performance, but also to achieve load balancing and mutual backup. Need to take advantage of disk cabinet storage technology (preferably san). For database services, it also requires the support of database software, which is more complicated. The WEB server or application server is relatively simple.

Load balancing: the services of the two servers are in the starting state, and the access queue is allocated through the front-end hardware. One of them fails, and the other automatically takes over, and the business is not interrupted; the solution is usually more expensive. Hundreds of thousands or so. (It is generally for application services, and there is no general version for database load balancing due to different interfaces.)

Reference:
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