CDH 5.13.1 Redhat 6.9 We wish to change the number of replications from the default of 3 copies to 2 on one particular folder in hdfs. After running this on one cluster: $ hdfs dfs -setrep -R 2 /backups and then doing a $ hdfs dfs -du / we saw that it freed the blocks very quickly and the output of fsck shows no "Over-replicated blocks": Status: HEALTHY  Total size:    149514016589 B  Total dirs:    27440  Total files:    128746  Total symlinks:        0  Total blocks (validated):    126355 (avg. block size 1183285 B)  Minimally replicated blocks:    126355 (100.0 %)  Over-replicated blocks:    0 (0.0 %)  Under-replicated blocks:    0 (0.0 %)  Mis-replicated blocks:        0 (0.0 %)  Default replication factor:    3  Average block replication:    2.3367577  Corrupt blocks:        0  Missing replicas:        0 (0.0 %)  Number of data-nodes:        3  Number of racks:        1 However on a bigger test system did the same command and even a day later still no change. $ hdfs fsck / shows "Over-replicated blocks" Status: HEALTHY  Total size:    56614841380 B  Total dirs:    7222  Total files:    113731  Total symlinks:        0  Total blocks (validated):    110143 (avg. block size 514012 B)  Minimally replicated blocks:    110143 (100.0 %)  Over-replicated blocks:    37439 (33.991264 %)  Under-replicated blocks:    0 (0.0 %)  Mis-replicated blocks:        0 (0.0 %)  Default replication factor:    3  Average block replication:    2.9921465  Corrupt blocks:        0  Missing replicas:        0 (0.0 %)  Number of data-nodes:        8  Number of racks:        1 The number of Over-replicated blocks has reduced slightly and seems stuck at 37439. I've manually restarted each datanode service, and later restarted the entire cluster. Still stuck at 37439. I found this comment from Jarsh J: |Then monitor the over-replicated blocks in Cloudera Manager via the below chart tsquery: | |SELECT excess_blocks WHERE roleType = NAMENODE | |This should show a spike and then begin a slow but steady drop back to zero over time, which you can monitor. but when I run this query it reports "excess_blocks" is 0. $ hdfs dfs -du / 22987202359  69376013863  /backups shows 3 copies still. How to get this data space cleared? Rebalance did nothing. thanks. ... View more