Installation guide

Parent, child, and sibling relationships among resources
The types of resources and the hierarchy of resources depend on the type of service you are
configuring.
The types of cluster resources are listed in Appendix C, HA Resource Parameters. Information about
parent, child, and sibling relationships among resources is described in Appendix D, HA Resource
Behavior.
2.6. Configuring max_luns
It is not necessary to configure max_luns in Red Hat Enterprise Linux 5.
In Red Hat Enterprise Linux releases prior to Red Hat Enterprise Linux 5, if RAID storage in a cluster
presents multiple LUNs, it is necessary to enable access to those LUNs by configuring max_luns (or
max_scsi_luns for 2.4 kernels) in the /etc/modprobe.conf file of each node. In Red Hat
Enterprise Linux 5, cluster nodes detect multiple LUNs without intervention required; it is not
necessary to configure max_luns to detect multiple LUNs.
2.7. Considerat ions for Using Quorum Disk
Quorum Disk is a disk-based quorum daemon, qdiskd, that provides supplemental heuristics to
determine node fitness. With heuristics you can determine factors that are important to the operation
of the node in the event of a network partition. For example, in a four-node cluster with a 3:1 split,
ordinarily, the three nodes automatically "win" because of the three-to-one majority. Under those
circumstances, the one node is fenced. With qdiskd however, you can set up heuristics that allow
the one node to win based on access to a critical resource (for example, a critical network path). If
your cluster requires additional methods of determining node health, then you should configure
qdiskd to meet those needs.
Note
Configuring qdiskd is not required unless you have special requirements for node health. An
example of a special requirement is an "all-but-one" configuration. In an all-but-one
configuration, qdiskd is configured to provide enough quorum votes to maintain quorum
even though only one node is working.
Important
Overall, heuristics and other qdiskd parameters for your Red Hat Cluster depend on the site
environment and special requirements needed. To understand the use of heuristics and other
qdiskd parameters, refer to the qdisk(5) man page. If you require assistance understanding
and using qdiskd for your site, contact an authorized Red Hat support representative.
If you need to use qdiskd, you should take into account the following considerations:
Clu st er n o d e vo t es
Each cluster node should have the same number of votes.
⁠Chapt er 2 . Before Config uring a Red Hat Clust er
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