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Achieving High Availability - Part 2 1 2 3 4 5 The warm standby server does not need to be a dedicated server. It can perform other functions in your environment. I would not mix other applications on the standby server. Other functions are not only feasible, but desirable. If you are using a backup/restore method, the standby server is a perfect candidate for handling most of your reporting needs. This offloads a large processing overhead from the primary and makes good use of the standby server. This simple act can also mean the difference between having to use the standby server when the primary fails or being able to use it for a reporting server all of the time. Every processor cycle that can be offloaded to another server is one less possibility of a failure occurring.If you have a warm standby configured with replication, this server is a perfect candidate for performing load balancing. You can load balance two ways. The first way would be to distribute processing evenly between the two servers, but process data modifications only on the primary. In this case, transactional replication can meet your needs. The second way is to distribute all operations, including modifications, to both servers. In this case, you could use either merge replication or transactional with immediate updating subscribers. If you are using this solution underneath a website, I would opt for transactional with immediate updating subscribers. This is simply because each database request is a new connection. Since it is a new connection, you can never guarantee which server that connection will be processed on. The last thing you want is to have the first connection enter an order on the standby and have the second connection come in a millisecond later to query that order and not have it exist because the second connection went to the primary. This will accomplish load balancing at the risk of losing customers which would be unacceptable. For web based applications where a latency is not an issue and for any other types of applications, I would use merge replication. I can sum up this choice in one word: -Validate. If you haven't played with merge replication or this option, it is worth a look just to give the replication group at Microsoft a huge pat on the back. This single feature is worth upgrading to 7.0 for any shop using replication. I've been dealing with replication for several years on multiple platforms and DBMSes and can say this is the most significant and sought after replication feature that has been introduced since I started using replication over 5 years ago. You can get an idea of what it offers from Books On-line. You'll have to go to the search table and type in "replmerg" in order to find it. Now that we have covered standby servers in relatively good detail, that only leaves three areas to cover in subsequent articles.
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