For people who faced with that type of problem. First of all you should understand the nature of the problem. To do that please read the description of the following issues: https://issues.apache.org/jira/browse/HDFS-8072 https://issues.apache.org/jira/browse/HDFS-9530 The following links will be useful to understand what block replica is: https://blog.cloudera.com/understanding-hdfs-recovery-processes-part-1/ https://blog.cloudera.com/understanding-hdfs-recovery-processes-part-2/ Solutions 1. Find the wrong software which often broke connection with Hadoop during the write or append processes 2. Try to change replication policy (risky) 3. Update Hadoop up to late version   You can't reset “Reserved Space for Replicas” without restart Hadoop services! ... View more