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.