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Clustring database

August 3, 2009
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Clustering :
Clustering is where two or more servers are configured to act as a single system. Clustering can improve the reliability and throughput of an Internet-based system. Troubleshooting and determining the root cause of problems also can be much simpler with clustering. However, clustering requires a great deal of technical knowledge if the system is to be properly set-up and maintained.
Clustering Benefits:

Clustering improves the reliability of Internet-based systems because it eliminates many of the single points of failure that are possible in a single server system. For example, with clustering you could have two or more web servers supporting your Internet site. If one of the servers fails your throughput might be impacted to some degree but the site would still be available on the second server. In a single server system your site would be offline if this happened.

The throughput of a system can be vastly improved with clustering because you can put a load balancer in the system that will send traffic to the least busy resource. This also means clustering can handle huge swings in volume that may occur during the day.

Clustering also makes it much easier to troubleshoot systems if properly configured. Instead of having many different items loaded on one server you can put similar programs on each server so it is easier to determine if a problem is related to an application, database, bandwidth, etc.

Drawback:

Because only one instance of SQL Server is being run on the virtual server, one server will always be in standby mode and idle. This means that you are not getting the most out of the money you used for the hardware

If failover occurs and one server is running both SQL Server instances, performance can be adversely affected. However, this slower performance is probably better than the virtual server totally being down. An additional drawback is that this configuration requires more licenses to be purchased than with an Active/Passive cluster. Because the cluster is running two active instances of SQL Server, you will be required to purchase the licenses for two separate server machines, which depending on your situation, may be a deterrent.

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