Zeus Load Balancer Overview
Introduction
The Zeus Load Balancer is an extremely powerful software-based approach to intelligently load-balance webservers. Available now as a separate package to the Zeus Web Server, it enables several webservers to be grouped together into a 'cluster', so that all the servers can work together to host the same websites. Incoming requests for pages are received by the Zeus Load Balancer and are distributed to individual servers in the cluster. The Balancer spreads out the work, ensuring that no one machine is overloaded.If a machine in the cluster was to fail, the Zeus Load Balancer will detect this and re-direct page requests onto the remaining machines. Similiarly, extra servers can easily be added to the cluster, even while it is running, in case extra performance is required.
You gain greatly enhanced performance and increased reliability / availability. Because the Zeus Load Balancer fully understands HTTP, the result is a cluster of webservers that far outperforms the simpler 'round-robin' DNS or hardware-based approaches to load balancing.
For details on how to obtain the Zeus Load Balancer, please contact sales@zeustechnology.com
Dual load balancers
For even greater fault-tolerance, two Zeus Load Balancers can be configured so that they both manage the same cluster of webservers. Incoming requests for webpages are split between the two Balancers by the use of round-robin DNS. If one Balancer should suffer a hardware failure, the other will automatically detect this and take over from it, so that to the outside world, the website continues operating unaffected.Configuration
Management of the Zeus Load Balancer and of the cluster of machines being controlled is made simple thanks to its close integration with the Zeus Admin Server.Terminology
Many of the terms in the documents are commonly used to mean different things in computing literature, so an explanation of terms used is given first:
Clustering
Multiple machines with identical configurations (a cluster) to which requests can be made. The cluster appears to be one coherent unit; configuration changes made with the admin server are updated on all machines in the cluster simultaneously.
Load balancing
In the simplest form, this is just optimising incoming requests to the least busy machine in a cluster, although the Zeus Load Balancer performs other calculations in order to achieve the optimal response time for all users of the cluster.
Fault-tolerance
The transparent takeover by a machine of another failed machine, with continuity of service maintained. If a back-end server in a cluster fails, requests will no longer be sent to it until it returns to service. The twin front-end balancer configuration means service will continue if a front-end machine's hardware fails.
Front end machines
The Zeus Load Balancers. These are positioned at the 'front' of the cluster, i.e. they are the machines first contacted by web browsers requesting pages from the cluster.
Back end machines:
The web servers running in the cluster. They are 'hidden' behind the Balancers, so that to each client web browser, the site appears to be one single webserver whereas it is in fact several machines.
Load Balancer topics