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.

HCL Notes® clients can access all Domino® cluster servers. HTTP clients (Internet browsers) can access only Domino® Web servers in a Domino® cluster.

The main benefits of clusters are:

• High availability of important databases

  When a hardware or software problem occurs, clustered servers redirect database open requests to other servers in the cluster to provide users with uninterrupted access to important databases. This process is called failover. Clusters provide failover for business-critical databases and servers, including pass-through server failover to other servers in the cluster. Failover also lets you perform server maintenance, such as hardware and software upgrades, with little negative effect on users.

• Workload balancing

  When users try to access databases on heavily used servers, Domino® can redirect the user requests to other cluster servers that aren't as busy so that the workload is evenly distributed across the cluster. Workload balancing of cluster servers helps your system achieve optimum performance, which leads to faster data access.

• Scalability

  As the number of users you support increases, you can easily add servers to a cluster to keep server performance high. You can also create multiple database replicas to maximize data availability, and you can move users to other servers or clusters as you plan for future growth. As your enterprise grows, you can distribute user accounts across clusters and balance the additional workload to optimize system performance within a cluster.

• Data synchronization

  A key to effective clustering is setting up replicas on two or more cluster servers so that users have access to data when a server is down or is being used heavily. Cluster replication ensures that all changes, whether to databases or to the cluster membership itself, are immediately passed to other databases or servers in the cluster. Thus, databases are continuously synchronized to provide high availability of information.

• Analysis tools

  Using the cluster analysis tools, as well as the log file, the Monitoring Configuration and Monitoring Results databases, and the server monitor, you can analyze cluster activity and make any changes necessary to improve performance.

• Ease of changing operating systems, hardware, or versions of Domino®

  When you want to change your hardware, operating system, or Domino® release, you can mark the clustered server as RESTRICTED so that requests to access a database on the server fail over to other cluster servers that contain replicas. This lets you make changes without interrupting the productivity of your users.

• Data backup and disaster planning

  You can set up a cluster server as a backup server to protect crucial data. You can prevent users from accessing the server, but cluster replication keeps the server updated at all times. You can even do this over a WAN so that the backup is in a different geographical location.

• Easy administration

  You can create a cluster with a few keystrokes. You can also add servers to a cluster, remove servers from a cluster, and move servers between clusters with a few keystrokes. In addition, you can drag and drop databases into a cluster and specify which cluster servers should receive replicas. You can also create multiple mail replicas and roaming file replicas for users when you register them, and you can monitor all the servers in a cluster simultaneously.

• Use of any hardware and operating system that Domino® supports

  You can set up a cluster using the same hardware you use for your Domino® servers. You do not need to use special hardware to create a Domino® cluster. In addition, the cluster can contain servers that use any operating system that Domino® supports.