There has been some debate regarding this, and the discussion seems to have come up more than once. "Dual primary is cool, but not >2 primary, right?" etc. Let me just write down the "official" stance here to remind everyone.
The "official" statement from Lars is:
Exactly two nodes could still work with two primaries in DRBD® 9 (so nor 3rd secondary either. exactly two nodes). But if you ever get concurrent writes (GFS2 layer messed up, fencing not working but pretending it was, whatever) it may behave "differently" (worse?) than 8.
Phil's stance is:
No, the wording should be: Dual primary is only supposed to be used for live migration of virtual machines.
(In my opinion it is not worth the effort to guarantee that all the corner cases for real dual primary work reliably, for a non existing market of GFS2/OCFS2 users)
In summary; no. Don't do dual primary with DRBD9 outside of live migration of VMs where the is some other component responsible for the live migration.
Published by DJV 2021-07-23