Global File System 2 or GFS2 is a shared disk file system for Linux computer clusters. GFS2 allows all nodes to have direct concurrent access to the same shared block storage. GFS2 has no disconnected operating-mode, and no client or server roles. All nodes in a GFS2 cluster function as peers. GFS2 supports up to 32 cluster nodes. Using GFS2 in a cluster requires hardware to allow access to the shared storage, and a lock manager to control access to the storage.
SUSE recommends OCFS2 over GFS2 for your cluster environments if performance is one of your major requirements. Our tests have revealed that OCFS2 performs better as compared to GFS2 in such settings.
To use GFS2, make sure
gfs2-utils
and a matching
gfs2-kmp-*
package for your
Kernel is installed on each node of the cluster.
The gfs2-utils
package provides
the following utilities for management of GFS2 volumes. For syntax
information, see their man pages.
GFS2 Utility |
Description |
---|---|
fsck.gfs2 |
Checks the file system for errors and optionally repairs errors. |
gfs2_jadd |
Adds additional journals to a GFS2 file system. |
gfs2_grow |
Grow a GFS2 file system. |
mkfs.gfs2 |
Create a GFS2 file system on a device, usually a shared device or partition. |
tunegfs2 |
Allows viewing and manipulating the GFS2 file system parameters such
as |
Before you can create GFS2 volumes, you must configure DLM and a STONITH resource.
You need to configure a fencing device. Without a STONITH
mechanism (like external/sbd
) in place the
configuration will fail.
Start a shell and log in as root
or equivalent.
Create an SBD partition as described in Procedure 11.3, “Initializing the SBD Devices”.
Run crm
configure
.
Configure external/sbd
as fencing device with
/dev/sdb2
being a dedicated partition on the shared
storage for heartbeating and fencing:
crm(live)configure#
primitive
sbd_stonith stonith:external/sbd \ params pcmk_delay_max=30 meta target-role="Started"
Review your changes with show
.
If everything is correct, submit your changes with
commit
and leave the crm live configuration with
exit
.
For details on configuring the resource group for DLM, see Procedure 17.1, “Configuring a Base Group for DLM”.
After you have configured DLM as cluster resources as described in Section 19.2, “Configuring GFS2 Services and a STONITH Resource”, configure your system to use GFS2 and create GFS2 volumes.
We recommend that you generally store application files and data files on different GFS2 volumes. If your application volumes and data volumes have different requirements for mounting, it is mandatory to store them on different volumes.
Before you begin, prepare the block devices you plan to use for your GFS2 volumes. Leave the devices as free space.
Then create and format the GFS2 volume with the
mkfs.gfs2
as described in
Procedure 19.2, “Creating and Formatting a GFS2 Volume”. The most important parameters for the
command are listed in Table 19.2, “Important GFS2 Parameters”. For
more information and the command syntax, refer to the
mkfs.gfs2
man page.
GFS2 Parameter |
Description and Recommendation |
---|---|
Lock Protocol Name ( |
The name of the locking protocol to use. Acceptable locking protocols are lock_dlm (for shared storage) or if you are using GFS2 as a local file system (1 node only), you can specify the lock_nolock protocol. If this option is not specified, lock_dlm protocol will be assumed. |
Lock Table Name ( |
The lock table field appropriate to the lock module you are using.
It is
clustername:fsname.
clustername must match that in the
cluster configuration file, |
Number of Journals ( |
The number of journals for gfs2_mkfs to create. You need at least one journal per machine that will mount the file system. If this option is not specified, one journal will be created. |
Execute the following steps only on one of the cluster nodes.
Open a terminal window and log in as root
.
Check if the cluster is online with the command crm
status
.
Create and format the volume using the mkfs.gfs2
utility. For information about the syntax for this command, refer to
the mkfs.gfs2
man page.
For example, to create a new GFS2 file system on
/dev/sdb1
that supports up to 32 cluster nodes,
use the following command:
root #
mkfs.gfs2 -t hacluster:mygfs2 -p lock_dlm -j 32 /dev/sdb1
The hacluster
name relates to
the entry cluster_name
in the file
/etc/corosync/corosync.conf
(this is the default).
You can either mount a GFS2 volume manually or with the cluster manager, as described in Procedure 19.4, “Mounting a GFS2 Volume with the Cluster Manager”.
Open a terminal window and log in as root
.
Check if the cluster is online with the command crm
status
.
Mount the volume from the command line, using the
mount
command.
If you mount the GFS2 file system manually for testing purposes, make sure to unmount it again before starting to use it by means of cluster resources.
To mount a GFS2 volume with the High Availability software, configure an OCF file
system resource in the cluster. The following procedure uses the
crm
shell to configure the cluster resources.
Alternatively, you can also use Hawk2 to configure the resources.
Start a shell and log in as root
or equivalent.
Run crm
configure
.
Configure Pacemaker to mount the GFS2 file system on every node in the cluster:
crm(live)configure#
primitive
gfs2-1 ocf:heartbeat:Filesystem \ params device="/dev/sdb1" directory="/mnt/shared" fstype="gfs2" \ op monitor interval="20" timeout="40" \ op start timeout="60" op stop timeout="60" \ meta target-role="Stopped"
Create a base group that consists of the dlm
primitive you created in Procedure 17.1, “Configuring a Base Group for DLM” and the
gfs2-1
primitive. Clone the group:
crm(live)configure#
group
g-storage dlm gfs2-1clone
cl-storage g-storage \ meta interleave="true"
Because of the base group's internal colocation and ordering, Pacemaker
will only start the gfs2-1
resource on nodes that also have a dlm
resource
already running.
Review your changes with show
.
If everything is correct, submit your changes with
commit
and leave the crm live configuration with
exit
.