Installation guide

An HA service is a group of cluster resources configured into a coherent entity that provides
specialized services to clients. An HA service is represented as a resource tree in the cluster
configuration file, /etc/cluster/cluster.conf (in each cluster node). In the cluster
configuration file, each resource tree is an XML representation that specifies each resource, its
attributes, and its relationship among other resources in the resource tree (parent, child, and sibling
relationships).
Note
Because an HA service consists of resources organized into a hierarchical tree, a service is
sometimes referred to as a resource tree or resource group. Both phrases are synonymous with
HA service.
At the root of each resource tree is a special type of resource — a service resource. Other types of
resources comprise the rest of a service, determining its characteristics. Configuring an HA service
consists of creating a service resource, creating subordinate cluster resources, and organizing them
into a coherent entity that conforms to hierarchical restrictions of the service.
Red Hat Cluster supports the following HA services:
Apache
Application (Script)
LVM (HA LVM)
MySQL
NFS
Open LDAP
Oracle
PostgreSQL 8
Samba
Note
Red Hat Enterprise Linux 5 does not support running Clustered Samba in an active/active
configuration, in which Samba serves the same shared file system from multiple nodes. Red
Hat Enterprise Linux 5 does support running Samba in a cluster in active/passive mode,
with failover from one node to the other nodes in a cluster. Note that if failover occurs,
locking states are lost and active connections to Samba are severed so that the clients
must reconnect.
SAP
Tomcat 5
There are two major considerations to take into account when configuring an HA service:
The types of resources needed to create a service
Red Hat Ent erprise Linux 5 Clust er Administ rat ion
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