To prevent disk corruption in case of accessing VG from 2 servers without efficient locking, you ca use mount guard. The only exception to this is mounting the filesystem read-only, where files or directories can't be changed.

In AIX 7100-01 and 6100-07 a new feature called “Mount Guard” has been added to prevent simultaneous or concurrent mounts. If a filesystem appears to be mounted on another server, and the feature is enabled, AIX will prevent mounting on any other server.

Mount Guard is not enabled by default, but is configurable by the system administrator. The option is not allowed to be set on base OS filesystems such as /, /usr, /var etc.

To turn on Mount Guard on a filesystem you can permanently enable it via /usr/sbin/chfs:

# chfs -a mountguard=yes /mountpoint /mountpoint is now guarded against concurrent mounts.

The same option is used with crfs when creating a filesystem.

To turn off mount guard:

# chfs -a mountguard=no /mountpoint /mountpoint is no longer guarded against concurrent mounts.

To determine the mount guard state of a filesystem:

# lsfs -q /mountpoint Name Nodename Mount Pt VFS Size Options Auto Accounting /dev/fslv34 – /mountpoint jfs2 4194304 rw no no

(lv size: 4194304, fs size: 4194304, block size: 4096, sparse files: yes, inline log: no, inline log size: 0, EAformat: v1, Quota: no, DMAPI: no, VIX: yes, EFS: no, ISNAPSHOT: no, MAXEXT: 0, MountGuard: yes)

The /usr/sbin/mount command will not show the mount guard state.

Filesystem Mounting and Mount Guard

When a filesystem is protected against concurrent mounting, and a second mount attempt is made you will see this error:

# mount /mountpoint mount: /dev/fslv34 on /mountpoint: Cannot mount guarded filesystem. The filesystem is potentially mounted on another node

After a system crash the filesystem may still have mount flags enabled and refuse to be mounted. In this case the guard state can be temporarily overridden by the “noguard” option to the mount command:

# mount -o noguard /mountpoint mount: /dev/fslv34 on /mountpoint: Mount guard override for filesystem. The filesystem is potentially mounted on another node.

chvg -N option is the one that prevent the varyon of the sharedvg

chvg -N n sharedvg :command to prevent varyon on two servers.