Installation guide

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVol00
# initrd /initrd-version.img
#boot=/dev/hda
default=0
timeout=5
serial --unit=0 --speed=115200
terminal --timeout=5 serial console
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" .
2.5. Considerat ions for Configuring HA Services
You can create a cluster to suit your needs for high availability by configuring HA (high-availability)
services. The key component for HA service management in a Red Hat cluster, rgmanager,
implements cold failover for off-the-shelf applications. In a Red Hat cluster, an application is
configured with other cluster resources to form an HA service that can fail over from one cluster node
to another with no apparent interruption to cluster clients. HA-service failover can occur if a cluster
node fails or if a cluster system administrator moves the service from one cluster node to another (for
example, for a planned outage of a cluster node).
To create an HA service, you must configure it in the cluster configuration file. An HA service
comprises cluster resources. Cluster resources are building blocks that you create and manage in the
cluster configuration file — for example, an IP address, an application initialization script, or a Red
Hat GFS shared partition.
An HA service can run on only one cluster node at a time to maintain data integrity. You can specify
failover priority in a failover domain. Specifying failover priority consists of assigning a priority level
to each node in a failover domain. The priority level determines the failover order — determining
which node that an HA service should fail over to. If you do not specify failover priority, an HA service
can fail over to any node in its failover domain. Also, you can specify if an HA service is restricted to
run only on nodes of its associated failover domain. (When associated with an unrestricted failover
domain, an HA service can start on any cluster node in the event no member of the failover domain is
available.)
Figure 2.1, “Web Server Cluster Service Example” shows an example of an HA service that is a web
server named "content-webserver" . It is running in cluster node B and is in a failover domain that
consists of nodes A, B, and D. In addition, the failover domain is configured with a failover priority to
fail over to node D before node A and to restrict failover to nodes only in that failover domain. The HA
service comprises these cluster resources:
IP address resource — IP address 10.10.10.201.
An application resource named " httpd-content" — a web server application init script
/etc/init.d/httpd (specifying httpd).
A file system resource — Red Hat GFS named "gfs-content-webserver".
Red Hat Ent erprise Linux 5 Clust er Administ rat ion
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