Kindly advice me on below queries.
What is the difference between cloudera navigator and kerberos security.
What is role of cloudera navigator in hadoop cluster security. Can we secure hadoop cluster without kerberos.
Where to use cloudera navigator and where to use kerberos.
Cloudera Navigator is used to track lineage of data. http://www.cloudera.com/products/cloudera-navigator.html
Using cloudera Navigator you will be in a position to track where and how a dataset was created.
Kerberos Security is used for authentication of the usage. http://web.mit.edu/kerberos/
Regarding the usecase :
It depends on what you wish to do.
If you want to track lineage then you will need Cloudera Navigator. If you want security then Kerberos will do.
Hope this answers your question.