Open file for append
Write data and sync.
After next log roll and editlog tailing in standbyNN close the append stream.
Call append multiple times on the same file, before next editlog roll.
Now abruptly kill the current active namenode.
Here block is missed..
this may be because of All latest blocks were queued in StandBy Namenode.
During failover, first OP_CLOSE was processing the pending queue and adding the block to corrupted block.