[root@xenmaster003 ~]# lvextend -L +50G /dev/drbd_sh1_vg0/cluster_files /dev/drbd3
  Extending logical volume cluster_files to 250.00 GB
  Logical volume cluster_files successfully resized
[root@xenmaster003 ~]# gfs2_grow -T /dev/drbd_sh1_vg0/cluster_files /cluster_files/
(Test mode--File system will not be changed)
FS: Mount Point: /cluster_files
FS: Device:      /dev/mapper/drbd_sh1_vg0-cluster_files
FS: Size:        52428798 (0x31ffffe)
FS: RG size:     65535 (0xffff)
DEV: Size:       65536000 (0x3e80000)
The file system grew by 51200MB.
FS: Mount Point: /cluster_files
FS: Device:      /dev/mapper/drbd_sh1_vg0-cluster_files
FS: Size:        52428798 (0x31ffffe)
FS: RG size:     65535 (0xffff)
DEV: Size:       65536000 (0x3e80000)
The file system grew by 51200MB.
gfs2_grow complete.
[root@xenmaster003 ~]# gfs2_grow /dev/drbd_sh1_vg0/cluster_files /cluster_files/
FS: Mount Point: /cluster_files
FS: Device:      /dev/mapper/drbd_sh1_vg0-cluster_files
FS: Size:        52428798 (0x31ffffe)
FS: RG size:     65535 (0xffff)
DEV: Size:       65536000 (0x3e80000)
The file system grew by 51200MB.
Error: The device has grown by less than one Resource Group (RG).
The device grew by 0MB.  One RG is 255MB for this file system.
gfs2_grow complete.
[root@xenmaster003 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/md2               57G  2.7G   51G   6% /
/dev/md0              251M   52M  187M  22% /boot
tmpfs                 7.7G     0  7.7G   0% /dev/shm
/dev/mapper/drbd_sh0_vg0-xen_shared
                       56G  259M   56G   1% /xen_shared
/dev/mapper/drbd_sh1_vg0-cluster_files
                      250G  145G  106G  58% /cluster_files