HDFS + change Block replication from 3 to 2

[#1]

hi all

in ambari dashboard we have HDFS Disk usage 100%

so we decided to decrease the Block replication from 3 to 2 , in order to free space

then we restart the HDFS service

but the HDFS Disk usage on ambari dashboard , still have 100%

do we miss here something

why HDFS isn't get free , regarding that we decrease the replication Block from 3 to 2?

[#2]

@Michael Bronson Setting replication to 2 will be applicable only for files you create now.

Use this command to decrease the hdfs size.

hadoop dfs -setrep -w 2 -R /