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Planning
Use this topic as an overview of planning task.
Planning a cluster
When planning a cluster, it is important to consider the performance and ability of your hardware. The cluster must have enough CPU power, memory, and disk space to handle the cluster traffic and the number of databases and replicas required.
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.
Clustering basics
All the servers in an HCL Domino® cluster continually communicate with each other to keep updated on the status of each server and to keep database replicas synchronized.

Planning
Use this topic as an overview of planning task.
- Roadmap for deploying Domino® servers
  Use this as a tool when planning how to integrate HCL Domino® into your existing environment.
- Planning server-to-server connections
  Servers must connect to each other to exchange data, for example to replicate databases and exchange mail. You can create connections between servers across a local area network (LAN) or wide area network (WAN), by using a pass-through server (a server that acts as an intermediary server between a client and its destination), or over the Internet. Create a Server Connection document whenever you need to establish any new or additional server connections. You can modify this document when necessary.
- Planning directory services
  HCL Domino® provides a range of directory service features.
- Planning a mail routing topology
  HCL Domino® offers you considerable flexibility in configuring your mail system infrastructure, allowing you to use HCL Notes® routing, SMTP routing, or both, for internal and external messages.
- Planning a cluster
  When planning a cluster, it is important to consider the performance and ability of your hardware. The cluster must have enough CPU power, memory, and disk space to handle the cluster traffic and the number of databases and replicas required.
  - 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.
    - Clustering basics
      All the servers in an HCL Domino® cluster continually communicate with each other to keep updated on the status of each server and to keep database replicas synchronized.
    - How failover works
      An HCL Domino® server cluster's ability to redirect requests from one server to another is called failover. When a user tries to access a database on a server that is unavailable or in heavy use, Domino directs the user to a replica of the database on another server in the cluster.
    - How workload balancing works
      By distributing databases throughout theHCL Domino® server cluster, you balance the workload in the cluster so that no server is overloaded.
    - The cluster components
      Several components -- the Cluster Manager, Cluster Database Directory, Cluster Database Directory Manager, Cluster Administrator, and Cluster Replicator -- work together to make clustering function correctly.
    - How replication works in a cluster
      Cluster replication is event-driven, rather than schedule-driven. When the Cluster Replicator learns of a change to a database, it immediately pushes that change to other replicas in the cluster. If there is a backlog of replication events, the Cluster Replicator stores these in memory until it can push them to the other cluster servers. If a change to the same database occurs before a previous change has been sent, the Cluster Replicator pools these changes and sends them together to save processing time.
    - Mail failover in a Domino® server cluster
      Depending on how your HCL Domino® server cluster is configured, mail fails over in one of several ways.
    - How calendars work in a cluster
      HCL Domino® supports clustering of calendars and the Free Time database. When clustered, the scheduling system works a little differently behind the scenes than when it is not clustered. However, these differences are not noticeable to users.
    - How operating system clusters work
      The method of clustering that HCL Domino® uses is called application clustering. Domino, which is an application, monitors the cluster and determines when failover and workload balancing should occur, based on parameters that you set. Another form of clustering is operating system clustering. In this form of clustering, the operating system monitors the cluster and determines when failover should occur. When failover occurs, the server (called a node) to which you fail over takes over the resources of the failed node, accesses the storage space the failed node was accessing, and runs the applications the failed node was running.
  - 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 the TCP/IP network
  The default TCP/IP configuration for an HCL Domino® server is one IP address that is globally bound, meaning that the server listens for connections at the IP addresses of all NICs on the computer. Global binding works as long as the computer does not have more than one IP address offering a service over the same assigned TCP port.
- Messaging overview
  The HCL Domino® mail system has three basic components: Domino mail servers, Domino mail files, and mail clients. The Domino mail server is the backbone of an organization's messaging infrastructure, acting both as an Internet mail server and an HCL Notes® mail server. Domino provides standards-based Internet messaging through its support of the Simple Mail Transfer Protocol (SMTP), Post Office Protocol version 3 (POP3), Internet Message Access Protocol (IMAP), and Multipurpose Internet Mail Extensions (MIME). At the same time, Domino supports Notes mail through the use of Notes routing protocols -- Notes remote procedure calls (NRPC) -- and the Notes rich text message format.
- Planning your Notes® client deployment
  Use the references listed here to plan for, install, upgrade to, and configure the HCL Notes® client.
- Planning security
  An important aspect of planning security for your Domino® environment is understanding the tasks and features involved with securing each type of resource.

Clustering basics

All the servers in an HCL Domino® cluster continually communicate with each other to keep updated on the status of each server and to keep database replicas synchronized.

Each server in a cluster contains cluster components that are installed with the Domino® Enterprise server. These components, and the Administration Process, perform the cluster management and monitoring tasks that run the cluster and let you administer the cluster. The components keep replica databases synchronized, and they communicate with each other to ensure that the cluster is running efficiently and smoothly. They also let you set limits for workload balancing, track the availability of servers and databases, and add servers and databases to the cluster.

To take advantage of failover and workload balancing, you distribute databases and replicas throughout the cluster. You do not need a replica of every database on every server. The number of replicas you create for a database depends on how busy the database is and how important it is for users to have constant access to that database. For some databases, you may not need to create any replicas; for others, you may need to create multiple replicas.