I would strongly suggest you look at HBase's snapshotting model as detailed at https://hbase.apache.org/book.html#ops.snapshots. The snapshot create process is very fast as it does NOT create a copy of the underlying HFiles on HDFS (just keeps HDFS snapshot "pointers" to them). Then you can use the ExportSnapshot process that will copy the needed underlying HFiles over to the second HBase cluster. This model won't utilize any extra space on the source cluster (well, delete the snapshot once you are done!) or on the target cluster as you'll have to get all those HFiles created which is what this process does. Good luck and happy HBasing!
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