6.1.1 Prerequisites for cluster system operations

SLM can operate in a logical host environment in a cluster system that supports failover. The prerequisites for running SLM in a logical host environment are that the allocation, deletion, and operation monitoring of the shared disk and logical IP addresses must be managed routinely by the cluster software.

SLM supports Windows Server Failover Cluster as the cluster software.

Important: Depending on the system configuration and environment setup, a cluster software program that is supported by SLM might not satisfy the prerequisites described here. Evaluate the system configuration and environment setup to make sure that all the prerequisites are satisfied.

Organization of this subsection

(1) Prerequisites for the logical host environment
(2) Prerequisites for the physical host environment
(3) Scope of SLM support

(1) Prerequisites for the logical host environment

To run SLM in a logical host environment, the following prerequisites for the shared disk and logical IP addresses must be satisfied.

Table 6‒1: Prerequisites for the logical host environment
Logical host component	Prerequisites
Shared disk	A shared disk that can inherit data from the active server to the standby server is available. The shared disk is allocated before SLM is started. Allocation of the shared disk is not released while SLM is running. Allocation of the shared disk is released after SLM has stopped. The shared disk is controlled in such a manner that it will not be accessed improperly from multiple nodes. Files are protected by means such as a file system with a journal function so that files are not deleted by events such as system shutdown. File contents are guaranteed and inherited in the event of a failover. Forced failover is supported, even while a process is using the shared disk. If a shared disk failure is detected, a program such as cluster software will manage the recovery processing, and there will be no need for SLM to be aware of the recovery processing. If SLM needs to be started or stopped as an extension of recovery processing, the cluster software must issue the stop and start requests to SLM.
Logical IP addresses	Inheritable logical IP addresses can be used for communication. A unique logical IP address can be obtained from any logical host name. The logical IP addresses have been allocated before SLM is started. The logical IP addresses will not be deleted while SLM is running. While SLM is running, the correspondence between logical host names and logical IP addresses will not be changed. The logical IP addresses will be deleted after SLM has stopped. If a network failure is detected, a program such as cluster software will manage the recovery processing, and there will be no need for SLM to be aware of the recovery processing. If SLM needs to be started or stopped as an extension of recovery processing, the cluster software must issues the stop and start requests to SLM.

To Page Top

(2) Prerequisites for the physical host environment

In a cluster system that runs SLM on a logical host, each server's physical host environment must satisfy the prerequisites described below.

Table 6‒2: Prerequisites for the physical host environment
Physical host component	Prerequisites
Server	The cluster consists of two server systems. Sufficient CPU performance is available for the processing that will be performed (for example, if multiple logical hosts are started, there is adequate CPU performance). Sufficient real memory capacity is available for the processing that will be performed (for example, if multiple logical hosts are started, there is adequate real memory capacity).
Disk	Files are protected by a means such as a file system with a journal function so that files are not deleted during events such as system shutdown.
Network	Communications can be performed using IP addresses corresponding to the physical host names (results of the `hostname` command) (a program such as the cluster software is not able to change settings that will disable communications). While SLM is running, the correspondence between host names and IP addresses will not be changed (by programs such as the cluster software or the name server). A LAN board supporting host names is given the top priority by the network bind settings (no other LAN board, such as one for heartbeat, is given the top priority).
OS and cluster software	The cluster software and its version are supported by SLM. The patches and service packs required by SLM and the cluster software have already been applied. Each server's environment is set up appropriately so that the same processing can continue in the event of a failover.

To Page Top

(3) Scope of SLM support

When SLM is run on a logical host in a cluster system, SLM controls only itself. The logical host environment (including shared disk allocation and inheritance of logical IP addresses) is managed by the cluster software.

If the prerequisites for the logical host environment and the physical host environment are not satisfied or there is any problem in controlling the logical host environment, SLM will not respond to problems that arise from SLM operations. For troubleshooting, see the documentation for the cluster software and the OS that control the logical host environment.

To Page Top