http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-user/201111.mbox/%3C12735A05C1926847AAFA701DD4474677090947@EAGF-ERFPMBX23.ERF.thomson.com%3E0.20.x 系ではバグがあるせいで、"Number of Under-Replicated Blocks" がやたら大きくなる場合があ…