Namenode to be in safemode while taking name node meta data and datanode backup ?

[#1]

Namenode to be in safemode while taking name node meta data and datanode backup ?

[#2]

Assuming by a NameNode backup you mean a simple 'hdfs dfsadmin -fetchImage' command, the NameNode does not need to be in a safe-mode to run it.

Am not sure what you mean by a DataNode backup. Data is replicated in HDFS, so a loss of single DataNode or a disk under a DataNode will not require backups to restore and will auto-heal.