Saturday, October 29, 2011

How to implement High Availability?

How to implement High Availability solution?

How to implement High Availability solution for your high traffic web pages or for your mission critical application?

You can use the new server and believe that the new server will not break. That may be true, but not later rely. You can use RAID. But this will only protect against disc crashes. If you drive controller but broke down as I mentioned in a previous article so you do not force anything. Probably best to design and implement server as High Available Cluster.

There are several solutions to this issue from different companies. Of course, every company claims that its solution is best.

Generally we can say that HA solved using certified hardware, software and configuration of these systems, an experienced professional should be resistant against unforeseen outages and hardware failures.

If we need to ensure the availability of a service or misssion critical application must use at least two computers. One computer will work and one for him to oversee. In case of failure of the working computer's function assumes that oversaw a computer. When it comes to recovery of a broken computer and the computer returns to its default settings.

HA Cluster can probably easiest to realize with the help of Heartbeat daemon or service. Heartbeat allows you to connect two computers to the cluster. For each machine is defined by a set of services, which has run on it. After starting the daemon will first try to communicate with the daemon on a second computer in the cluster, if it finds that it works, starts services that are run. He regularly with a demon on the other computer diagnostic messages exchanged. If the demon finds in the course of action that the other computer did not respond to him long enough, begins to act. Verifies that the second computer is really dead, and then your computer starts up services that run on a crashed computer. Sometimes it even takes over its IP address. Accidents should be seen more than a very short outage necessary to start the service. After recovering crashed computer services will start again on the original computer.

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