Installation guide

Resource Behavior.
5. 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.
6. Considerations 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:
Cluster node votes
Each cluster node should have the same number of votes.
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