Installation guide

title Red Hat Enterprise Linux Server (2.6.18-36.el5)

root (hd0,0)

kernel /vmlinuz-2.6.18-36.el5 ro root=/dev/VolGroup00/LogVol00

console=ttyS0,115200n8 acpi=off

initrd /initrd-2.6.18-36.el5.img

In this example, acpi=off has been appended to the kernel boot command line — the line

starting with "kernel /vmlinuz-2.6.18-36.el5".

Example 2.11. Kernel Boot Command Line with acpi=off Appended to It

4. 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.

5. 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.

Chapter 2. Before Configuring a Red Hat Cluster