Installation guide

GFS/GFS2 is a native file system that interfaces directly with the Linux kernel file system interface
(VFS layer). When implemented as a cluster file system, GFS/GFS2 employs distributed metadata and
multiple journals. Red Hat supports the use of GFS/GFS2 file systems only as implemented in Red
Hat Cluster Suite.
Note
Although a GFS/GFS2 file system can be implemented in a standalone system or as part of a
cluster configuration, for the RHEL 5.5 release and later, Red Hat does not support the use of
GFS/GFS2 as a single-node file system. Red Hat does support a number of high-performance
single-node file systems that are optimized for single node, and thus have generally lower
overhead than a cluster file system. Red Hat recommends using those file systems in
preference to GFS/GFS2 in cases where only a single node needs to mount the file system.
Red Hat will continue to support single-node GFS/GFS2 file systems for existing customers.
Note
The maximum number of nodes supported in a Red Hat Cluster deployment of GFS/GFS2 is
16.
GFS/GFS2 is based on a 64-bit architecture, which can theoretically accommodate an 8 EB file
system. However, the maximum size of a GFS/GFS2 file system supported by Red Hat is 25 TB. If your
system requires GFS/GFS2 file systems larger than 25 TB, contact your Red Hat service
representative.
Red Hat GFS/GFS2 nodes can be configured and managed with Red Hat Cluster Suite configuration
and management tools. Red Hat GFS/GFS2 then provides data sharing among GFS/GFS2 nodes in
a Red Hat cluster, with a single, consistent view of the file system name space across the GFS/GFS2
nodes. This allows processes on multiple nodes to share GFS/GFS2 files the same way that
processes on a single node can share files on a local file system, with no discernible difference.
A GFS/GFS2 file system must be created on an LVM logical volume that is a linear or mirrored
volume. LVM logical volumes in a Red Hat Cluster are managed with CLVM (Cluster Logical Volume
Manager). CLVM is a cluster-wide implementation of LVM, enabled by the CLVM daemon, clvmd,
running in a Red Hat cluster. The daemon makes it possible to manage logical volumes via LVM2
across a cluster, allowing the cluster nodes to share the logical volumes. For information about the
LVM volume manager, refer to Logical Volume Manager Administration.
Note
When you configure a GFS/GFS2 file system as a cluster file system, you must ensure that all
nodes in the cluster have access to the shared file system. Asymmetric cluster configurations
in which some nodes have access to the file system and others do not are not supported.This
does not require that all nodes actually mount the GFS/GFS2 file system itself.
1.6. Clust er Logical Volume Manager
Red Hat Ent erprise Linux 5 Clust er Suit e Overview
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