Dual Primary OCFS2 DRBD encountered split-brain. Is recovery always going to be manual in this case?

Solution 1:

IMHO you already choose the best SB-policy for DRBD. So in your case there had to be changes on the same part of the filesystem (i.e. DRBD-block) on BOTH sides.

So in that case - yes - you have to resolve that manually.

The question that arises to me is why did these concurrent accesses happen?

You should investigate into that direction. If network is down there should be no access at one side, so "discard zero changes" should help - but it did not.

Apart from that your should prevent split brains by having two or more INDEPENDENT network connections. I always use three of them on my clusters.