What is a Domino cluster?
An HCL Domino cluster is a group of two or more servers that provides users with constant access to data, balances the workload between servers, improves server performance, and maintains performance when you increase the size of your enterprise. The servers in a cluster contain replicas of databases that you want to be readily available to users at all times. If a user tries to access a database on a cluster server that is not available, Domino opens a replica of that database on a different cluster server, if a replica is available. Domino continuously synchronizes databases so that whichever replica a user opens, the information is always the same.
Cluster benefits and requirements
This section explains what an HCL Domino cluster is, how a cluster can benefit you, and the hardware and software requirements for setting up and using a cluster.
How Domino clustering works
This section explains how HCL Domino clustering works for Notes® clients and Domino servers. This section also describes operating system clusters and how Domino clusters work in conjunction with operating system clusters.
Determining how many Domino servers to include in a cluster
Adding HCL Domino servers to the cluster increases the cluster's ability to balance the workload so that no server becomes overloaded and performance stays high. However, if servers use too many server tasks, CPU-intensive applications, and replicas, adding servers can decrease performance because of the additional amount of cluster traffic required to keep databases synchronized on all servers.
Determining the number and placement of replicas in a cluster
There are two major reasons to create a replica for a database in a cluster -- to provide constant availability of the data and to distribute the workload between multiple servers. Before you create replicas in a cluster, consider how frequently users access a database and their need for data redundancy. If a database is extremely busy or its availability is extremely important, create multiple replicas and locate them on your most reliable servers. For databases that are not very busy and whose constant availability is not important, you may not want to create any replicas at all. A server log file, for example, does not need to have a replica on another server.
Distributing databases in a cluster
The way you distribute databases significantly affects workload balancing, as well as the performance of your equipment.
Determining whether to create a private LAN for your cluster
To make a busy cluster more efficient, you can create a private network for your cluster. To do so, you install an additional network interface card in each cluster server and connect these network interface cards through a private hub or switch.
Clustering over a wide area network
A cluster over a wide are network (WAN) works the same way as a cluster on a LAN. However, if you have a low-speed WAN, you should consider disabling cluster replication. Instead, use scheduled replication more frequently than usual, such as every hour. This reduces WAN traffic, bottlenecks, and the cost of continual transmission.
Fault recovery in a cluster
Fault recovery is the ability of an HCL Domino server to clean up and restart itself after a failure. Fault recovery works well in a Domino cluster. If there is no Domino server to fail over to, fault recovery still ensures that users will have constant access to their data. Even if users fail over to another cluster server, fault recovery increases availability because the failed server becomes available again. In addition, depending on the workload balancing parameters you've set, some users will fail back to the original server when they open new databases.
Planning to use the Internet Cluster Manager (ICM)
Plan the cluster that the Internet Cluster Manager (ICM) will service. Then plan where to run the ICM itself and how many ICMs to run.