A blockreport is a list of all HDFS data blocks that correspond to each of the local files, and sends this report to the NameNode.
- when the DataNode starts up (It scans through its local file system)
- at specified interval ?
A Blockreport contains the list of data blocks that a DataNode is hosting. Each block has a specified minimum number of replicas.
Trigger a block report
with HDFS - DFSAdmin, see the options -triggerBlockReport [-incremental]''