C H A P T E R 2 | Site Balancing Methods |
fulfillment of a specific type or types of traffic as being crucial to their business goals. (Available with the 7140/7170, 7180 2.3 release.)
•Least Connections - The Least Connections method sends requests to the site with lowest number of connections. This method permits the most efficient management of requests that are likely to require connections of long duration, such as FTP. (Available with the 7140/7170 and 7180 releases.)
•CPU Utilization of Local Load Balancer - This method directs clients to the site whose load balancer has the lightest workload. The benefit of this method is most evident when used with sites performing
(Available with the 7170 2.2.1 release.)
Managing Unequal Site Servers
There is a “factor” command to determine a threshold factor in the event of two unequal servers. (see config dns zones <zonename> hostnames <hostname> siteservices <siteservicename> factor in Chapter 5, “CLI Reference.”)
The 7190 determines which IP address to return for a hostname, based on the performance of the IP address and port at a site. The
1.Determine the metric(s) with the smallest value.
2.Determine whether any remaining service(s) are close enough to this best value to also be considered. The quantification of “close enough” is the factor. A factor of 0 means consider only services with the best value.
3.Randomly choose from all the services identified in the first two steps.
A good example of the usefulness of this “close enough” threshold factor is when two unequal servers are deployed behind different load balancers. Server A may be capable of handling 3000 connections per second. Server B may also be capable of handling that many connections per second, but is also serving more sites than Server A. The realistic connection limit of Server B may therefore only be about 500 connections per second. If Server A has 900 connections and Server B has 400 connections, then Server B is the site with the least number of connections, although it is already 80% loaded while Server A is only 30% loaded. The better choice would be to give the traffic to server A. However, the 7190 has no knowledge of the actual
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