Chapter 1. GFS Overview
Red Hat GFS is a cluster file system that is available with Red Hat Cluster Suite. Red Hat GFS nodes are configured and managed with Red Hat Cluster Suite configuration and management tools. Red Hat GFS provides data sharing among GFS nodes in a Red Hat cluster. GFS provides a single, consistent view of the file-system name space across the GFS nodes in a Red Hat cluster. GFS allows applications to install and run without much knowledge of the underlying storage infrastructure. GFS is fully compliant with the IEEE POSIX interface, allowing applications to perform file operations as if they were running on a local file system. Also, GFS provides features that are typically required in enterprise environments, such as quotas, multiple journals, and multipath support.
GFS provides a versatile method of networking your storage according to the performance, scalability, and economic needs of your storage environment. This chapter provides some very basic, abbreviated information as background to help you understand GFS. It contains the following sections:
1.1. New and Changed Features
This section lists new and changed features included with the initial release of Red Hat Red Hat GFS 6.1 and Red Hat GFS 6.1 for Red Hat Enterprise Linux 4 Update 2.
For information about upgrading from GFS 6.0 to GFS 6.1, refer to Appendix A Upgrading GFS.
 | Note |
|---|---|
Multipath GNBD is not available with Red Hat GFS 6.1. That is, device mapper multipath (dm-multipath) cannot use GNBD. GNBD without multipath is available. |
New and Changed Features with the Initial Release of Red Hat GFS 6.1
Cluster infrastructure provided by Red Hat Cluster Suite — This release of Red Hat GFS uses the cluster infrastructure of Red Hat Cluster Suite, taking advantage of the Red Hat Cluster Suite configuration file and cluster graphical user interface (GUI), system-config-cluster. For information about configuring and managing Red Hat Cluster Suite, refer to Red Hat Cluster Suite Configuring and Managing a Cluster. Previous versions of Red Hat GFS provided a cluster infrastructure that was exclusive to GFS (even though used with Red Hat Cluster Suite). Additionally, configuration files in earlier versions of Red Hat GFS were created and maintained via text editors only (that is, no GUI was available).
Red Hat Cluster Suite lock architectures — Via Red Hat Cluster Suite, GFS can use the following lock architectures:
DLM (Distributed Lock Manager), new for Red Hat GFS 6.1 — DLM provides lock management throughout a Red Hat cluster, requiring no nodes to be configured as lock management nodes (contrasted to GULM, which does require certain nodes to be configured as lock management nodes).
GULM (Grand Unified Lock Manager) — A client/server lock architecture that is compatible with Red Hat GFS 6.0.
Nolock — For single node operation only.
New volume manager, LVM2 — The pool volume manager in earlier releases of Red Hat GFS is replaced with LVM2 for this release. LVM2 is used in conjunction with CLVM (Cluster Logical Volume Manager). This release provides a tool to convert GFS 6.0 pool volumes to the LVM2 format. For information about converting pool volumes to the LVM2 format, refer to Appendix A Upgrading GFS.
Enhanced gfs_fsck performance and changes to the gfs_fsck command — The gfs_fsck function performs 10 times as fast as gfs_fsck in earlier GFS releases. (This enhancement has been included in a recent update to Red Hat GFS 6.0, also.) In addition, the enhanced gfs_fsck function includes changes to certain command options. For more information about changes to the command options, refer to Section 5.12 Repairing a File System.
Withdraw individual mount points — Allows individual GFS mount points to gracefully discontinue operations on a node without causing that node to panic. This feature provides the ability to continue operations with unaffected file systems on that node. The feature can be overridden to allow a node to panic, thereby providing more information for troubleshooting. For more information, refer to the mount command option, oopses_ok, in Table 5-2
Increased storage supported — Red Hat GFS supports 8 terabytes of storage per GFS file system. For more information about Red Hat GFS requirements, refer to Chapter 2 System Requirements
New and Changed Features with Red Hat GFS 6.1 for Red Hat Enterprise Linux 4 Update 2
Red Hat GFS 6.1 for Red Hat Enterprise Linux 4 Update 2 supports iSCSI and multipath iSCSI. That is, device mapper multipath (dm-multipath) can use iSCSI.