Quoting Henrique Fernandes <sf.rique@gmail.com>:
for drbd you only need a heartbeat i guess.
Fencing is not needed for drbd, though recommended.
But to use gfs2 you need fence device, ocfs2 does not require once, like the ocfs2 driver takes care, it reboots if it thinks it is desyncronized
gfs2 technically requires fencing, since it technically requires a cluster, and red hat clustering requires fencing. Some people "get around this" by using "manual" fencing, though this is "not recommended for production" as it could result in a machine staying down until manual intervention, which usually conflicts with the "uptime" desire for a cluster... But that is up to the implementor to decide on...
[]'sf.rique
-- Eric Rostetter The Department of Physics The University of Texas at Austin
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