Shared storage and pure software method in dual-machine hot standby

Dual-machine hot with two implementation modes, one is based on shared storage devices, the other is not shared storage devices, generally referred to as a pure software approach.

Dual-Machine hot standby based on storage sharing is the most standard scheme for dual-machine hot standby.

For this approach, two servers are used, shared storage devices (either a disk array cabinet or a storage Area network SAN). Two servers can be used in different ways, such as standby, master-slave, parallel, and so on. During the work process, the two servers will be a virtual IP address to provide services, depending on the mode of work, the service request sent to one of the server to bear. At the same time, the server detects the performance of another server through the heartbeat line, which is now often used to establish a private network. When one server fails, another server makes a decision based on heartbeat detection and switches to take over the service. For the user, this process is fully automated, completed in a very short time, and thus does not affect the business. Because of the use of shared storage devices, the two servers are actually using the same data, which is managed by a dual-computer or cluster software.

For pure software, it is through the support of the mirror dual-computer software, the data can be replicated to another server in real time, so the same data on both servers exist on a single, if a server failure, you can switch to another server in time.

There is another scenario in the pure software approach, where the server simply provides the application service and does not save the data (for example, only some calculations are used for the application server). In this case, there is also no need to use shared storage devices, which should be included in the Load balancing field