Hey all.

We've been seeing this warning on one of our clusters:

2015-10-18 14:28:52,898 WARN  [ValidationExecutor:14] org.apache.cassandra.db.context.CounterContext invalid global counter shard detected; (4aa69016-4cf8-4585-8f23-e59af050d174, 1, 67158) and (4aa69016-4cf8-4585-8f23-e59af050d174, 1, 21486) differ only in count; will pick highest to self-heal on compaction

From what I've read and heard in the IRC channel, this warning could be related to not running upgradesstables after upgrading from 2.0.x to 2.1.x.  I don't think we ran that then, but we've been at 2.1 since last November.  Looking back, the warnings start appearing around June, when no maintenance had been performed on the cluster.  At that time, we had been on 2.1.3 for a couple of months.  We've been on 2.1.10 for the last week (the upgrade was when we noticed this warning for the first time).

From a suggestion in IRC, I went ahead and ran upgradesstables on all the nodes.  Our weekly repair also ran this morning.  But the warnings still show up throughout the day.

So, we have many questions:
We're pretty lost here, so any help would be greatly appreciated.