Need to be able to evacuate a datanode
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Key: HADOOP-3034
URL: https://issues.apache.org/jira/browse/HADOOP-3034
Project: Hadoop Core
Issue Type: Improvement
Reporter: Ted Dunning
It would be very helpful if there were some way to evacuate data from one or
more nodes.
This scenario arise fairly often when several nodes need to be powered down at
nearly the same time. Currently, they can only be taken down a few at a time
(n-1 nodes at a time where n is the replication factor) and then you have to
wait until all files on these nodes have been replicated.
One implementation would be to be to allow the nodes in question be put into
read only mode and mark all blocks on those nodes as not counting as
replicants. This should cause the namenode to copy these blocks and as soon as
fsck shows no under-replicated files, the nodes will be known to be clear for
power-down.
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