Cloud computing is emerging as a promising technology for outsourcing of data and quality of data services. However, information which is sensitive when upload on cloud eventually cause privacy problems. Data encryption provides security of data to some level, but at the cost of compromised efficiency. This paper focus on addressing data privacy problems. For the first time, the privacy issue is formulated from the aspect of similarity relevance of data and scheme robustness. Privacy of data is not assured if server-side ranking based on order-preserving encryption is maintained.