Installation guide

5.2.3 Hosts file

The /etc/hosts file for each cluster member should contain an entry defining localhost. If the

external host name of the system is defined on the same line, the host name reference should

be removed.

Additionally, each /etc/hosts file should define the local interconnect of each cluster member.

5.3 Storage Configuration

5.3.1 Multipathing

Storage hardware vendors offer different solutions for implementing a multipath failover

capability. This document focuses on the generic multipath device mapper approach. Please

consult your storage hardware vendor for the correct and supported multipath configuration.

5.3.2 Device Mapper Multipath

The device mapper multipath plugin (DM multipath) provides greater reliability and

performance by using path failover and load balancing. In HA scenarios, cluster servers can

use multiple paths to the shared storage devices. Normally these devices are presented as

multiple device files (/dev/sdXX)

DM-Multipath creates a single device that routes I/O to the underlying devices according to

the multipath configuration. It creates kernel block devices (/dev/dm-*) and corresponding

block devices (with persistent names) in the /dev/mapper directory.

The multipath configuration file can also be used to set storage specific attributes. These

multipath specific settings are usually obtained from the storage vendor and typically

supersede the default settings.

5.3.3 CLVM

In RHCS, LVM managed shared storage must be controlled by High Availability resource

manager agents for LVM (HA-LVM) or the clustered logical volume manager daemon (clvmd/

CLVM). Single instance LVM must not be used for shared storage, as it is not cluster aware

and can result in data corruption. In this document, CLVM will be used as it allows

active/active storage configurations. This allows the use of GFS and secondly failover

scenarios are handled more easily.

Note that the qdisk partition cannot be managed by CLVM as this would overwrite the quorum

label assigned to the device.

When using CLVM, the clvmd must be running on all nodes. This can be accomplished by

enabling the clvmd init script. Please note, that the core cluster must be up and running,

before clvmd can be started.

# chkconfig clvmd on

# service clvmd start