Recently I want to upgrade our cluster from 2.6.5 to 3.1.3 but failed.so I rollback the version to old.but some strange things hanppend .our cluster's datanode can't report the block's situation to the the Active NameNode. so the datanode throw this exception " " I don't know why. The datanode throw this problem all the time. And the NameNode Web UI show the "There are xxx missing blocks. The following files may be corrupted" the information but the number of missing blocks still rising。。。。really scary  I don't know what happend to our cluster.. ....     ... View more