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

Software Component
gfs.ko
lock_dlm.ko
lock_nolock.ko
Table 1.1. GFS Software Subsystem Components

1.4. Before Setting Up GFS

Before you install and set up GFS, note the following key characteristics of your GFS file systems:
GFS nodes
Determine which nodes in the Red Hat Cluster Suite will mount the GFS file systems.
Number of file systems
Determine how many GFS file systems to create initially. (More file systems can be added later.)
File system name
Determine a unique name for each file system. 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.
File system size
GFS is based on a 64-bit architecture, which can theoretically accommodate an 8 EB file system.
However, the current supported maximum size of a GFS file system is 25 TB. If your system
requires GFS file systems larger than 25 TB, contact your Red Hat service representative.
When determining the size of your file system, you should consider your recovery needs. Running
the gfs_fsck command on a very large file system can take a long time and consume a large
amount of memory. Additionally, in the event of a disk or disk-subsytem failure, recovery time
is limited by the speed of your backup media. For information on the amount of memory the
gfs_fsck command requires, see
Journals
Determine the number of journals for your GFS file systems. One journal is required for each node
that mounts a GFS file system. Make sure to account for additional journals needed for future
expansion, as you cannot add journals dynamically to a GFS file system.
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 GFS, 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.
Description
Kernel module that implements the GFS file system and is
loaded on GFS cluster nodes.
A lock module that implements DLM locking for GFS. It plugs
into the lock harness, lock_harness.ko and communicates
with the DLM lock manager in Red Hat Cluster Suite.
A lock module for use when GFS is used as a local file system
only. It plugs into the lock harness, lock_harness.ko and
provides local locking.
Section 3.14, "Repairing a File
Before Setting Up GFS
System".
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