We use GFS2/rgmanager/DRBD and KVM for our cloud infrastructure.
I don't know what sort resource manager OCFS2 has; but gfs2 rgmanager is great and supports live migration; which work flawlessly.
I have been meaning to try out GPFS but have not got around to testing this; I was going to setup gpfs nodes in the existing kvm/gfs2 setup as vm guests.
Overall: Very reliable, some performance concerns with GFS2 locking between nodes even with rate limiting disabled.
[root@core-01 ~]# ./ping_pong /gfs2-00/test 3
2159 locks/sec
[root@core-01 ~]# ./ping_pong /gfs2-00/test 3
1336 locks/sec
[root@core-02 ~]# ./ping_pong /gfs2-00/test 3
1333 locks/sec
- One node pclock rw test "./ping_pong -rw /gfs2-00/test 3"
[root@core-01 ~]# ./ping_pong -rw /gfs2-00/test 3
2192 locks/sec
- Two node pclock rw test "./ping_ping -rw /gfs2-00/test 3"
[root@core-01 ~]# ./ping_pong -rw /gfs2-00/test 3
2 locks/sec
[root@core-02 ~]# ./ping_pong -rw /gfs2-00/test 3
2 locks/sec
I attempted to document some of our work:
http://wiki.samba.org/index.php/6.0:_DRBD#6.5._DRBD_8.0_GFS2_Primary.2FPrimary_Clustered_Filesystem