Shulou(Shulou.com)06/03 Report--

Why does the server have to do dual hot backup? What are the benefits of dual-computer hot backup?

Dual hot standby especially refers to the hot standby (or high availability) based on two servers in a high availability system. It is named dual hot standby because it is widely used in China. According to the switching mode in work, dual hot standby is divided into active-standby mode (Active-Standby mode) and dual-host mode (Active-Active mode). Active-standby mode means that a server is in a business activation state (i.e. Active state). The other server is in the standby state of the service (that is, the Standby state). The dual-host mode means that two different services are active and standby to each other on the two servers (that is, Active-Standby and Standby-Active status).

Scheme

The three main ways to make up the dual-computer hot backup are: based on shared storage (disk array), full redundancy and replication.

For server administrators, server failure may be the most serious problem, because there are many reasons for server failure, including equipment failure, operating system failure, and software failure. When there is a failure of the server, it is necessary to troubleshoot the server one by one to make the server run normally, at least for dozens of minutes, and then for dozens of hours. This is not to recover the loss caused by the server failure, at this time, the dual hot standby plays a key role in the server. Dual hot standby especially refers to the hot standby (or high availability) based on two servers in a high availability system. It is named dual hot standby because it is widely used in China. According to the switching mode in work, dual hot standby is divided into active-standby mode (Active-Standby mode) and dual-host mode (Active-Active mode). Active-standby mode means that a server is in a business activation state (i.e. Active state). The other server is in the standby state of the service (that is, the Standby state). The dual-host mode means that two different services are active and standby to each other on the two servers (that is, Active-Standby and Standby-Active status). For some important systems, it is difficult for users to endure such a long service interruption. Therefore, it is necessary to use dual-computer hot standby to avoid long-term service interruption and ensure the long-term and reliable service of the system. The correct way to decide whether to use dual-computer hot backup is to analyze the importance of the system and the tolerance of service interruption, so as to decide whether to use dual-computer hot backup. That is, how long your users can tolerate resuming the service, and how much impact it will have if the service cannot be restored. When considering dual-computer hot backup, it should be noted that in general, dual-computer hot backup will have a switching process, which may take about one minute. During the switching process, the service may be interrupted for a short time. However, when the handover is complete, the service will resume normally. Therefore, the dual-computer hot standby is not seamless and uninterrupted, but it can ensure that the normal service can be restored quickly in the event of system failure, and the business will not be affected. If there is no dual-computer hot backup, in the event of a server failure, there may be a service interruption for several hours, which may have a serious impact on the business. Another point to emphasize is that the concept of server failure is much higher than that of switches and storage devices. The reason is that the server is a much more complex device than switches and storage devices, and it is also a complex system including hardware, operating system and application software system. Not only equipment failure may cause service interruption, but also software problems may also cause the server to fail to work properly. It is also noted that although other protective measures of the server, such as disk array (RAID) and data backup, can protect user data to a great extent, they can not replace the role of dual-computer hot backup.

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