Prerequisites

The following requirements and limitations apply for installations using server redundancy:

• A cluster can have up to ten LIMs.
• A cluster can have only one standby server.
• It is possible to have as many clusters as there are LIMs in the system (with a maximum of one standby server per LIM server).
• A standby server can belong to only one cluster.
• A LIM server can belong to only one cluster.
• All servers in a cluster must reside on the same subnet. Gratuitous ARP is used in the network to announce that a standby server has taken over the alias IP address of a faulty regular server. (ARP is a link layer protocol, operating on the local subnet.)
• The Alias IP address must be on the same subnet as the base IP address.
• A standby server must have performance enough to be able to replace any regular server in the cluster.
• A standby server must have enough free hard disk space to store two data backups (system database data included) of each regular server in the cluster.
• There must be enough bandwidth within a cluster for efficient transfer of data backups to the standby server.
• Failover behavior preloaded is used only for clusters consisting of one regular and one standby server.