Posted by: Charles Tryon
on August 19, 2005 03:39 AM
Remember that there are at least two fundamental reasons for load balancing -- reliability (fault tolerance) and throughput. In the first case, it's critical to eliminate any single point of failure. If you are really interested in redundance, then you should be looking at distinct, geographically separated server locations, with a hot DR somewhere else. Of course, there's always a balance of how much money you have to spend vs. how much it's going to cost you if something goes down.
On the flip side, there's balancing in order to spread out a load between servers to eliminate a bottleneck. For example, if you have a data driven Web app, you may balance between two or more app servers (if they are the bottleneck), but tie into one big database. You run the database on RAID disks to give some sort of redundancy there (most common failure in a database box), but if you're not pushing the DB that hard, it may be able to handle multiple App servers hitting it.
So, as always, "It depends on what you are looking for..."
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Reliability vs. Throughput
Posted by: Charles Tryon on August 19, 2005 03:39 AMOn the flip side, there's balancing in order to spread out a load between servers to eliminate a bottleneck. For example, if you have a data driven Web app, you may balance between two or more app servers (if they are the bottleneck), but tie into one big database. You run the database on RAID disks to give some sort of redundancy there (most common failure in a database box), but if you're not pushing the DB that hard, it may be able to handle multiple App servers hitting it.
So, as always, "It depends on what you are looking for..."
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