【 Weak current College 】 camputer FAQs

Standby is the hub server will be installed to the backup of two servers, and at the same time, only one server running. Here we compare the concern to make the answer, I hope will be helpful to everyone.

Q: can explain what is a hot standby?

A: the so-called hot standby, is the hub server will be installed to the backup of two servers, and at the same time, only one server running. When running a server fails to start, another backup server will quickly start automatically and run (generally 2 minutes), thus ensuring the whole network uptime! hot standby works in practice is for the entire network System Center Server provides a failback capabilities.

Q: what time need hot standby?

A: this question is actually quite simple, General server to a life-long work, their work is absolutely not backed up. Therefore, the decision to use standby, I think it should first of all, the importance of the system, and end users on the service interruption for consideration of the degree of tolerance, and then to decide whether to use a hot standby. For example, network users up to tolerate long recovery service if the service cannot be quickly restored will lead to what kind of consequences, and so on.

Q: have RAID technology and data backup technology, it is also necessary to make hot standby?

Answer: this is not a clear distinction between RAID and backup all important data backup can only be solved! system problems after recovery; and RAID technology to the author's experience and can only solve the problem of the hard disk. We know that there is a problem when the server itself, regardless of the device's hardware or software system that will result in service disruption, and the RAID and backup technology just does not resolve the problems of avoiding disruption in service. Therefore, for high security needs, continuous and reliable application service network system, standby or very important. In fact, we can think of it this way: If your server is broken, you take the time to restore it to work properly so that you can understand the importance of hot standby!

Q: hot standby and differences between clusters?

A: conceptually, hot standby belong to a cluster. Clusters generally includes two categories: one category is pure application server cluster, that is, each application server has access to a unified database server, but he does not need some file-sharing, storage, etc., this cluster is relatively simple. The other type is a database server of the standby, standby, typically two servers at the same time using a shared storage device, and in General, take home, along the way (there is also a high-end system with the parallel manner, that is, two servers at the same time provide services).

Q: how to use the database services hot standby?

A: through software way hot standby. That is, do not use shared storage device, which is the native data directly in the flow between multiple hosts. Obviously, this way the biggest advantage is that saving expensive storage equipment investment, but its disadvantage is not difficult to find: produces data inconsistency, or affect the rate of database read.

We see this as an example: If a service disruption to switch to a backup server, you may have a small amount of already host completed transactions in preparation machine is not yet implemented. With the backup data recovery, backup machine startup, and subsequent actions already undertaken, the lost packet to find it quite difficult. In this way, the applicable for lost a small amount of data is not very sensitive system.

Here mention standard solution, which is based on a shared storage device and a two-computer software for hot standby. It can unattended cases provide fast switch, and no data loss, and purchase storage equipment investment is also relatively high.

Q: how to select and implement the hot standby configuration scheme?

A: 1. application-driven, careful analysis. For high availability.

2. consider using hot standby database or application server cluster, or backup software.

3. Select the identification of specific equipment, software, models, etc. The author here remind everyone that different software or hard drives, and other storage devices, there is a compatibility between them, so before you buy should consult professional, do not appear have dual machine software procurement related storage device is not compatible with such phenomena exist.

4. in the implementation is complete, be sure to test it to ensure that works fine, but it should be noted that in the course of regular running on the system is able to test the normal switch.