Related information: http://iweb.com/dedicated-server/cluster
Load balancers are configured in active/passive mode with an open source software called HAProxy. Please note that only one load balancer is required to do the work, but to ensure redundancy and availability, we use another server as a backup to the primary load balancer. In the event of a service interruption of the primary load balancer, the secondary load balancer will take over. An alert will be sent to our systems administrators who will investigate.
The load balancing is configured by default in a way that the 'balanced IP' is balanced over web servers on port 80 (HTTP). Your domain(s) must absolutely point to that IP address. The balancing mode is configured to "source", meaning that a client having a distinct source IP address will always be redirected to the same web server. This option is necessary when the websites use PHP sessions. If you do not require any PHP sessions, we could change the mode to "round-robin" which would cause the balancing to be done sequentially through the list of available web servers one after the other and when the end of the list is reached, the traffic is sent to the first server of the list and the loop starts again.
The load balancers are also acting as firewalls. Every time you need to open a new port on your web servers, you need to open the same port on the load balancers and forward the connection to the web servers. Because we don't usually give access to load balancers (except in really rare cases) to clients, you will need to contact us each time you want to make modifications to the configuration. In order to support your managed high availability web hosting cluster solution as well and as fast as possible, we do not provide any load balancer access to our customers. If you require access to maintain the cluster solution yourself, we will give you the credentials of the load balancers. However, we will not be able to provide support for the solution anymore.
Once you are done uploading and configuring your web site on the cluster, you can ask for a performance review from our systems administrators. team. They will use a stress test on your web site and modify the load balancers' configuration to optimize the general throughput and responsiveness of the solution. This service requires an additional fee for the duration of the analysis of a system administrator. Please contact us regarding the fees.