Before Setting Up Gfs2 - Red Hat ENTERPRISE LINUX 5 - GLOBAL FILE SYSTEM 2 Manual

Chapter 1. GFS2 Overview
Note
When you configure a GFS2 file system as a cluster file system, you must ensure that all
nodes in the cluster have access to the shared storage. Asymmetric cluster configurations
in which some nodes have access to the shared storage and others do not are not
supported. This does not require that all nodes actually mount the GFS2 file system itself.
This chapter provides some basic, abbreviated information as background to help you understand
GFS2. It contains the following sections:
Section 1.1, "Before Setting Up GFS2"
•
Section 1.2, "Differences between GFS and GFS2"
•

1.1. Before Setting Up GFS2

Before you install and set up GFS2, note the following key characteristics of your GFS2 file systems:
GFS2 nodes
Determine which nodes in the Red Hat Cluster Suite will mount the GFS2 file systems.
Number of file systems
Determine how many GFS2 file systems to create initially. (More file systems can be added later.)
File system name
Determine a unique name for each file system. The name must be unique for all lock_dlm
filesystems over the cluster, and for all filesystems (lock_dlm and lock_nolock) on each local
node. Each file system name is required in the form of a parameter variable. For example, this
book uses file system names mydata1 and mydata2 in some example procedures.
Journals
Determine the number of journals for your GFS2 file systems. One journal is required for each
node that mounts a GFS2 file system. GFS2 allows you to add journals dynamically at a later
point as additional servers mount a filesystem. For information on adding journals to a GFS2 file
Section 3.7, "Adding Journals to a File
system, see
GNBD server nodes
If you are using GNBD, determine how many GNBD server nodes are needed. Note the hostname
and IP address of each GNBD server node for setting up GNBD clients later. For information on
using GNBD with GFS2, see the Using GNBD with Global File System document.
Storage devices and partitions
Determine the storage devices and partitions to be used for creating logical volumes (via CLVM) in
the file systems.
Note
You may see performance problems with GFS2 when many create and delete operations
are issued from more than one node in the same directory at the same time. If this causes
performance problems in your system, you should localize file creation and deletions by a
node to directories specific to that node as much as possible.
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System".