Hi-
We're working in an environment where we'd like to add a new DataNode and quickly begin leveraging it, usually after detection of high load at the rest of our DataNodes. However, most of the methods I can find regarding placing pre-existing blocks on a new DataNode involve operations which are liable to perform unnecessary IO at the established DataNodes, such as: 1. Increasing replica count 2. Adding and removing a file 3. Global rebalance with a low threshold Is there any capability currently built in to force unidirectional movement of blocks to a targeted DataNode? This would be ideal for us because we already assume established DataNodes are under significant load, and we want to begin using the new DataNode with as minimal inter-DataNode block traffic as possible. I wanted to confirm the lack of this capability with you folks before trying to extend the Balancer class (http://hadoop.apache.org/hdfs/docs/r0.21.0/api/org/apache/hadoop/hdfs/serve r/balancer/Balancer.html). Thanks! -Ben
