HDFS-3479 backported HDFS-3335 to branch-1. However, the recovery mode feature in branch-1 is dramatically different from the recovery mode in trunk since the edit log implementations in these two branch are different. For example, there is UNCHECKED_REGION_LENGTH in branch-1 but not in trunk.
Edit Log Toleration:
HDFS-3521 added this feature to branch-1 to remedy UNCHECKED_REGION_LENGTH and to tolerate edit log corruption.
There are overlaps between these two features. We study potential further improvement in this issue.