Clustering Linux Servers with the Concurrent Deployment of HP Serviceguard Linux and Red Hat Global File System for RHEL5, October 2008

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Executive Summary
Organizations today are deploying critical applications on Linux clusters that require high
availability, ease of cluster management, and access to large pools of stored information. HP
Serviceguard for Linux provides high availability for applications running on a cluster of servers.
Red Hat’s Global File System (GFS) enables a cluster of Linux servers to simultaneously read and
write to a single shared file system on a Storage Area Network (SAN). Together, HP Serviceguard
for Linux and Red Hat GFS provide a best-of-breed, complete availability solution, from
applications to data, for the most mission-critical datacenter workloads.
Organizations that deploy both HP Serviceguard for Linux and Red Hat GFS on the same set of
servers need to be confident that these two clusters will operate concurrently in both normal
operation and during failures.
HP has tested and validated the ability, to have Serviceguard for Linux and Red Hat GFS (1) for
Red Hat Enterprise Linux 5 (RHEL5) co-exist on the same set of servers
Introduction
Organizations have gained confidence in the robust and maturing Linux environment such that
they are targeting inexpensive Linux servers to deploy complex and critical tasks on Linux. These
tasks include data management, large scale file-serving, and business processing applications.
These functions require clustering multiple Linux servers together, all of which need access to the
same storage pool. They also require that the applications deployed on the cluster be highly
available and not vulnerable to any single point of failure.
HP Serviceguard for Linux clusters a number of Linux servers and makes application services
available despite hardware or software failures or the planned downtime required for
maintenance or system upgrades. HP Serviceguard for Linux can respond to single or, sometimes,
multiple failures within a cluster. When it detects the failure of a node, it fails over applications
running on that node to other nodes in the cluster. The applications are restarted on the new
nodes by HP Serviceguard for Linux.
The Red Hat Cluster Suite (RHCS) for Red Hat Enterprise Linux 5 (RHEL5) is an integrated set of
software components that can be deployed in a variety of configuration. The cluster infrastructure
is a major component of RHCS that provides functions for nodes to work together as a cluster:
configuration-file management, membership management, Lock management, and fencing. Red
Hat GFS provides cluster file system for use with Red Hat Cluster Suite which allows multiple
nodes to share storage at a block level as if the storage were connected locally to each cluster
node. It enables multiple Red Hat Enterprise Linux servers to simultaneously read and write to a
single shared file system on the SAN. This increases performance and reduces management
complexity by eliminating the need for multiple copies of data. Red Hat GFS uses the Distributed
Lock Management (DLM), provided by RHCS, to synchronize access to file system metadata on
shared storage.
When HP Serviceguard for Linux and Red Hat GFS are both deployed on the same set of servers,
they act together when a failure occurs to quickly bring the application up on the new node.
Without GFS, HP Serviceguard for Linux moves the application package over to the new node
and mounts the file system that the application needs. When deployed together, Red Hat GFS will
have already made this file system visible to the new server and the file system can be used
immediately after GFS has gone through its recovery, with no additional time lost for file system
checks.
(1) The Red Hat GFS for RHEL5 uses Openais as the central cluster membership and messaging system which is completely different from
what was used in RHEL4.