Hi All:
I elected to take a node out of one of our grids for service. Naturally HDFS
recognized the loss of the DataNode and did the right stuff, fixing replication
issues and ultimately delivering a clean file system.
So now the node I removed is ready to go back in service. When I return it to
service a bunch of files will suddenly have a replication of 4 instead of 3.
My questions:
1. Will HDFS delete a copy of the data to bring replication back to 3?
2. If (1) above is yes, will it remove the copy by deleting from other nodes,
or will it remove files from the returned node, or both?
The motivation for asking the questions are that I have a file system which is
extremely unbalanced - we recently doubled the size of the grid when a few
dozen terabytes already stored on the existing nodes. I am wondering if an
easy way to restore some sense of balance is to cycle through the old nodes,
removing each one from service for several hours and then return it to service.
Thoughts?
Thanks in Advance,
C G
