This was a little non intuitive to me so I’ll document the procedure. What confused me is that, unlike most UNIXish filesystem, GPFS stores the mount path as a parameter in the filesystem metadata.

First use mmlsfs to find the block device name for the filesystem.

# mmlsfs all

File system attributes for /dev/foo:
=========================================
flag                value                    description
------------------- ------------------------ -----------------------------------
 -f                 131072                   Minimum fragment size in bytes
 -i                 512                      Inode size in bytes
 -I                 32768                    Indirect block size in bytes
 -m                 1                        Default number of metadata replicas
 -M                 2                        Maximum number of metadata replicas
 -r                 1                        Default number of data replicas
 -R                 2                        Maximum number of data replicas
 -j                 cluster                  Block allocation type
 -D                 nfs4                     File locking semantics in effect
 -k                 all                      ACL semantics in effect
 -n                 32                       Estimated number of nodes that will mount file system
 -B                 4194304                  Block size
 -Q                 none                     Quotas enforced
                    none                     Default quotas enabled
 --filesetdf        No                       Fileset df enabled?
 -V                 12.10 (3.4.0.7)          File system version
 --create-time      Wed Feb  8 18:34:14 2012 File system creation time
 -u                 Yes                      Support for large LUNs?
 -z                 No                       Is DMAPI enabled?
 -L                 4194304                  Logfile size
 -E                 Yes                      Exact mtime mount option
 -S                 No                       Suppress atime mount option
 -K                 whenpossible             Strict replica allocation option
 --fastea           Yes                      Fast external attributes enabled?
 --inode-limit      18300928                 Maximum number of inodes
 -P                 system                   Disk storage pools in file system
 -d                 nsd1;nsd2                Disks in file system
 -A                 yes                      Automatic mount option
 -o                 none                     Additional mount options
 -T                 /gpfs/bar                Default mount point
 --mount-priority   0                        Mount priority

Before attempting to modify the filesystem, you need to make sure that it unmounted on the cluster.

# mmumount /gpfs/bar -a
Wed Apr  4 17:50:07 MST 2012: mmumount: Unmounting file systems ...

The mount point can be modified with themmchfs command.

# mmchfs /dev/foo -T /net/bar
mmchfs: Propagating the cluster configuration data to all
  affected nodes.  This is an asynchronous process.

Then remount the filesystem on it’s new mountpoint.

# mmmount /net/bar -a
Wed Apr  4 17:51:57 MST 2012: mmmount: Mounting file systems ...