MiniDFSCluster's enabledManagedDfsDirsRedunancy flag should be ported to branch-2. Certain tests rely on it to get full coverage-- for example, TestNameNodeRecovery and TestFSEditLogLoader.
Just to give an example, if we're using redundant edit log directories, a test like this may succeed for the wrong reasons:
1. screw up edit log directory
2. run recovery
3. test that we can start NN
With redundant edit log directories and edit log failover, step 1 is a no-op because we can just fail over to the other directory. So we're not really testing what we need to test. This was supposed to be ported over to branch-2 from trunk with the other stuff from
HDFS-3049, but was not.