- Red Hat Enterprise Linux (RHEL) with the Resilient Storage Add-On
Useful References and Guides
This policy guide describes Red Hat's policies around the mounting of
gfs2 filesystems. Users of
gfs2 should adhere to these policies in order to be eligible for support from Red Hat with the appropriate product support subscriptions.
Mounting requirements: Any cluster node that is mounting or has mounted a
gfs2 filesystems is required to have
gfs2-utils installed in order for a withdraw to complete successfully . For more information then see the following: What is a GFS2 withdrawal in a RHEL Resilient Storage cluster?
gfs2 filesystems can only be mounted within a single cluster: Any single
gfs2 filesystem can only be mounted within a single cluster at a time. If a
gfs2 filesystem is mounted anywhere, that filesystem can only be simultaneously mounted by another member of the same cluster.
gfs2 filesystem cannot be mounted by nodes from different clusters, or by a node in a cluster and a non-cluster member.
gfs2 mounting procedures: Red Hat makes available several methods to mount
gfs2 filesystems, but only supports the following methods of activating a
gfs2 filesystem on a host. Other methods may not receive assistance from Red Hat:
- RHEL 8, 7, or 6: Mounting via the
mount -t gfs2or
mount.gfs2command, either with the filesystem configured in
/etc/fstabor providing the mount parameters directly to the command.
- RHEL 8, 7, or 6: Mounting via a
- RHEL 6: Mounting via an
- RHEL 6: Mounting by starting the
gfs2init service with the filesystem configured in
Note: With RHEL 8 or 7, Red Hat recommends mounting
gfs2 via a
Filesystem resource in the pacemaker cluster, as detailed here. When mounting
gfs2 via a managed cluster resource, that filesystem should not be defined in
gfs2 makes available a few different lock protocols that can be defined in the filesystems superblock or specified at mount time via an option or flag. Red Hat only provides support for two such protocols in RHEL Resilient Storage deployments, each with its own conditions:
gfs2filesystem must be mounted with this protocol if it is to be mounted across several hosts simultaneously. Each host mounting a
gfs2filesystem with this protocol must be an active, quorate member of a RHEL High Availability cluster and must be running
dlm_controld- started by a
controldcluster-managed resource in a RHEL 8 or 7 cluster or by the
cmaninit service in RHEL 6.
lock_nolock- This protocol allows a
gfs2filesystem to be mounted on a host without it being an active, quorate member of a cluster, or without it running
dlm_controld. However, only a single host can mount a
gfs2file system at a time if this protocol is in use. Red Hat will only provide support or assistance with
gfs2filesystems that are using
lock_nolockunder the following conditions:
- Backups: Red Hat can assist with usage of
lock_nolockas a temporary protocol for the purpose of backing up the filesystem's contents.
- Emergency recovery: Red Hat can assist with usage of
lock_nolockif it is deployed as a temporary measure to gain access to a filesystem under emergency conditions where the cluster or
dlm_controldservice is unable to facilitate mounting with
lock_dlm. For continued assistance from Red Hat with a
gfs2mount, there must be a reasonable expectation that filesystem will be returned to a
lock_dlmconfiguration once the emergency has passed and problematic conditions can be resolved.
- Backups: Red Hat can assist with usage of
gfs2 without an active, quorate cluster:
gfs2 can only be mounted outside of an active, functioning cluster by using the
lock_nolock protocol. See the above Lock protocols policy for conditions applicable to mounting a
gfs2 filesystem with this protocol without having a functional cluster.
- For a procedure to mount
gfs2without an active, quorate cluster, see: How to mount a GFS2 filesystem when quorum is lost or from a host that is not a member of the cluster on RHEL?
localflocks mount option:
gfs2 provides a
localflocks option at mount time that influences it to allow the kernel VFS layer to do all
fcntl (POSIX) file locking, instead of handling these through
gfs2's clustered-locking schemes. Red Hat only provides support for a
gfs2 filesystem that uses this option if it is only being mounted on a single node at a time. Any usage of
localflocks in which the filesystem gets mounted by multiple nodes simultaneously disqualifies that filesystem from receiving assistance from Red Hat.
gfs2 with SELinux: Special policies apply to usage of
gfs2 with SELinux.
gfs2 on only some nodes:
gfs2 does not require that all members of the cluster mount the filesystem. It can be mounted on a single node if desired, some subset of the total cluster, or all nodes.