So, we need to increase the following OCFS2 partition which sits on a drbd volume (which sits on lvm2 volume).
The grow steps have to be taken in the right order: lvm2, drbd and ocfs2.

This tutorial comes in text (below) and in youtube video (also below).
Enjoy ;)

Check out my channel for other interesting videos.

1. Increase LVM partition on ALL NODES

Command: lvresize -L+20G /dev/dockervg/data

22:24:07 root@sonic:~# df -h /docker/DATA
Filesystem      Size  Used Avail Use% Mounted on
/dev/drbd0      100G   92G  8.3G  92% /docker/DATA
22:24:58 root@sonic:~# lvscan | grep data
  ACTIVE            '/dev/dockervg/data' [100.00 GiB] inherit
22:25:12 root@sonic:~# pvscan | grep dockervg
  PV /dev/sdb1   VG dockervg        lvm2 [150.00 GiB / 34.50 GiB free]
22:26:16 root@sonic:~# lvresize -L+20G /dev/dockervg/data
  Size of logical volume dockervg/data changed from 100.00 GiB (25600 extents) to 120.00 GiB (30720 extents).
  Logical volume dockervg/data successfully resized.
22:26:26 root@sonic:~# lvscan | grep data
  ACTIVE            '/dev/dockervg/data' [120.00 GiB] inherit

22:15:39 root@jupiter:~# lvscan | grep data
  ACTIVE            '/dev/dockervg/data' [100.00 GiB] inherit
22:15:49 root@jupiter:~# pvscan | grep dockervg
  PV /dev/sdb1   VG dockervg        lvm2 [150.00 GiB / 29.50 GiB free]
  Total: 3 [179.75 GiB] / in use: 3 [179.75 GiB] / in no VG: 0 [0   ]
22:15:54 root@jupiter:~# lvresize -L+20G /dev/dockervg/data
  Size of logical volume dockervg/data changed from 100.00 GiB (25600 extents) to 120.00 GiB (30720 extents).
  Logical volume dockervg/data successfully resized.
22:16:09 root@jupiter:~# lvscan | grep data
  ACTIVE            '/dev/dockervg/data' [120.00 GiB] inherit

2. Increase DRBD partition on ONE NODE

Command: drbdadm resize dockerdata

22:27:30 root@sonic:~# drbdadm resize dockerdata
22:27:58 root@sonic:~# cat /proc/drbd
version: 8.4.7 (api:1/proto:86-101)
srcversion: F9342B04878A5D3C98CAB6D 
 0: cs:SyncSource ro:Primary/Primary ds:UpToDate/Inconsistent C r-----
    ns:28664141 nr:85711265 dw:114213910 dr:169548504 al:14361 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:d oos:20962160
	[>....................] sync'ed:  0.1% (20468/20480)M
	finish: 3:01:57 speed: 1,872 (1,872) K/sec

As you can see, sync started so you will have to wait for it to finish.

07:21:13 root@sonic:~# cat /proc/drbd
version: 8.4.7 (api:1/proto:86-101)
srcversion: F9342B04878A5D3C98CAB6D 
 0: cs:Connected ro:Primary/Primary ds:UpToDate/UpToDate C r-----
    ns:49740791 nr:87059269 dw:115676404 dr:194735194 al:14390 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:d oos:0

3. Increase OCFS2 filesystemon ONE NODE

Command: tunefs.ocfs2 -S /dev/drbd0

08:08:26 root@sonic:~# df -h /docker/DATA
Filesystem      Size  Used Avail Use% Mounted on
/dev/drbd0      100G   92G  8.2G  92% /docker/DATA
08:08:53 root@sonic:~# tunefs.ocfs2 -S /dev/drbd0
08:09:08 root@sonic:~# df -h /docker/DATA
Filesystem      Size  Used Avail Use% Mounted on
/dev/drbd0      120G   92G   29G  77% /docker/DATA

08:05:22 root@jupiter:~# df -h /docker/DATA
Filesystem      Size  Used Avail Use% Mounted on
/dev/drbd0      120G   92G   29G  77% /docker/DATA