Typically a load balancing method or strategy is used to decide how the load balancer chooses where to send the request. There are many strategies available depending on the vendor, however a few common ones are listed below:
Round robin:Â The most Â simple method, each server takes a turn.
Least number of connections:Â The load balancer will keep track of the number of connections a server has and send the next request to the server with the least connections.
Weighted:Â Typically servers are allocated a percentage capability as one server could be twice as powerful as another.Â Weighted methods are useful if the load balancer does not know the real and actual performance of the server.
Fastest response time:Â This method is normally only available on more advanced products. The request will be sent to the fastest responding server.
Server agent:Â A client is installed on the server that communicates with the load balancer. This is sometimes required when you are using a basic load balancer that has direct server return. I.e. it does not know how many actual connections the server has or how well it is responding as it does not get the responses from the servers.
Methods such as server agent and weighted try to guess what the performance should be like for the next request whilst methods such as fastest response time actually know what the server is doing in real time