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From Allen Wittenauer <awittena...@linkedin.com>
Subject Intelligence of decommission
Date Fri, 28 Aug 2009 20:07:05 GMT

As I sit here and wait for node decommission to finish, I was wondering
about the intelligence of the decision making.  [The name nodes, not mine.
:) ]

Let's say I have the following scenario:

I have two files.  Both files consist of one block with a replication factor
of three.  I decommission two nodes.  File #1 has two of its replicas on the
two nodes I am decommissioning.  File #2 has only one of its replicas on one
of the two nodes I am decommissioning.

Is the block with two replicas on the two nodes I am decommissioning given
priority?  How does the name node decide which blocks to re-replicate first?


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