Major Description
ksck checks that all tablet servers can be connected to, but during this check it doesn't validate that the expected tablet server ID matches the ID of the server which is connected to.
So if you have a 3 node cluster, wipe a tserver's data dirs and restart it, ksck will say something like 'successfully connected to 4 tablet servers', because it connects to the wiped tserver twice.
CC r1pp3rj4ck who expressed interest in fixing this.