This sounds like HDFS-5080, which is going to be fixed in CDH4.5.   On earlier versions, you can either use rsync, or shut down the active NN and use bootstrapStandby to work around the issue. ... View more

1. You can find out why the namenode is in safemode with "hdfs dfsadmin -safemode get"   2. I don't understand-- can you be more detailed?  What are you out of, memory or disk space?   3. Is the replication factor greater than the number of datanodes?   4. is the DFS down?   Colin ... View more