Hi Mehul
Some of the blocks it was managing are deleted/modified?
The namenode will asynchronously replicate the blocks to other datanodes in order to maintain the replication factor after a datanode has not been in contact for 10 minutes.
The size of the blocks are now modified say from 64MB to 128MB?
Block size is a per-file setting so new files will be 128MB, but the old ones will remain at 64MB.
What if the block replication factor was one (yea not in most deployments but say incase) so does the namenode recreate a file once the datanode rejoins?
(assuming you didn't perform a decommission) Blocks that lived only on that datanode will be declared "missing" and the files associated with those blocks will be not be able to be fully read, until the datanode rejoins.
George
