10.1.2 Prerequisites for cluster use

JP1/Service Support runs in the logical host environment of a cluster system, and supports failover. As the prerequisites for JP1/Service Support that runs in a logical host environment, the cluster software must normally control assignment and deletion of the shared disk and logical IP address and monitoring of behavior.

Note:: Even if JP1/Service Support supports a cluster software program, that program might not satisfy the prerequisites described here. This depends on the system configuration and environment settings. Therefore, consider the system configuration and environment settings to make sure that the cluster software can satisfy the prerequisites.

Organization of this subsection

(1) Prerequisites for a logical host environment
(2) Prerequisites for a physical host environment
(3) The scope supported by JP1/Service Support

(1) Prerequisites for a logical host environment

If you run JP1/Service Support in a logical host environment, the following prerequisites regarding the logical IP address and shared disk must be satisfied.

Table 10‒1: Prerequisites for a logical host environment
Component of a logical host	Prerequisites
Shared disk	The available shared disk can be taken over from the active node by the standby node. The shared disk must be assigned before installation of JP1/Service Support. Only the cluster software is allowed to release the assignment of the shared disk while JP1/Service Support is running. The shared disk's assignment will be released after JP1/Service Support is uninstalled. The shared disk is controlled so that it cannot be used by multiple nodes. Data written in the files must be certainly taken over when a failover occurs. Even if some processes are using the shared disk when a failover occurs, the failover can be forcibly conducted. If a failure in the shared disk is detected, JP1/Service Support does not have to care for recovery processing. The cluster software or some other method must be used to control recovery processing. If JP1/Service Support must be stopped or started due to a delay in recovery processing, the cluster software must request JP1/Service Support to stop or start.
Logical IP address	The logical IP address used for communication must be taken over. The logical IP address corresponding to the logical host name must be uniquely determined. The logical IP address must be assigned before installation of JP1/Service Support. The logical IP address must not be deleted while JP1/Service Support is running. The correspondence between the logical host name and the logical IP address must not be changed while JP1/Service Support is running. The logical IP address can be deleted after JP1/Service Support is uninstalled. If a network failure is detected, JP1/Service Support does not have to care for recovery processing. The cluster software or some other method must be used to control recovery processing. If JP1/Service Support must be stopped or started due to a delay in recovery processing, the cluster software must request JP1/Service Support to stop or start.

If the conditions in Table 10-1 are not satisfied, a problem might occur in JP1/Service Support operations. For example, the following problems might occur:

If the data written by the active node becomes corrupted when a failover occurs:

JP1/Service Support will incur problems, such as errors, data missing, or failure of startup, and will not operate normally.
If recovery processing is not done in response to a failure of a LAN board:

Communication errors will occur and JP1/Service Support will not operate normally until the LAN board is switched by the cluster software or other control methods, or a failover occurs to switch the server to another server.

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(2) Prerequisites for a physical host environment

In a cluster system in which JP1/Service Support is used on a logical host, the physical host environment for each server must satisfy the following prerequisites.

Table 10‒2: Prerequisites for a physical host environment
Component of a physical host	Prerequisites
Servers	A cluster configuration is established using two or more servers.
Network	Communication is available with the IP address corresponding to the physical host name (the results of the `hostname` command). (The cluster software or other processes must not make communication unavailable.)^# The correspondence between the host name and the IP address must not change while JP1/Service Support is running. (The cluster software and name server must not change that correspondence.) The LAN board corresponding to the host name takes the highest priority for the network binding settings (default setting). (Another LAN board, such as the one for heartbeat, must not take priority.)
OS and cluster software	The cluster software and its version are supported by JP1/Service Support. The environment for each server is appropriately configured so that processing can continue after a failover.

#: Communication using the IP address that corresponds to the physical host name (the host name displayed by the hostname command) might not be possible for some combinations of cluster software.

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(3) The scope supported by JP1/Service Support

If you use JP1/Service Support on a logical host of a cluster system, the scope controlled by JP1/Service Support is only the behavior of JP1/Service Support itself. The control of the logical host environment (the shared disk and logical IP address) and the trigger to start and stop JP1/Service Support depend on the control of the cluster software.

If the above prerequisites for the logical and physical host environments are not satisfied, or if the control of the logical host environment has a problem, problems in the behavior of JP1/Service Support are not supported. In this case, resolve the problem by using the cluster software that controls the logical host environment or by using the OS.

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