Your budget ? Do you prefer to build a NAS box on your own or prefer to buy a ready made solution ? Anyway, you can have a look at WD Sentinel DX4000 16TB. It's a pre configured Nas box.
It's cheaper on ebay [ about 10k ] but better to buy from amazon as it's a amazon fulfilled product :
Amazon.in: Buy WD 16TB WD Sentinel DX4000 Small Business Network File Storage Server iSCSI NAS Online at Low Prices in India | WD Reviews & Rating