backup tools used in datacenter replication

http://blog.mozilla.com/data/2011/02/04/migrating-hbase-in-the-trenches/

backup tools among datacenters :
fault tolerance : generic exceptions should be caught inside backup's mapreduce job
relative path : change path of source file. It is not a imporant feature, because DFS provide renanming function
run in update mode : source file list is changing through process of backup