do i need to install any software on storage, that's called vStorage API???
There is no specila package to installed, vSphere Storage API is avilable for license edition
vSphere Storage API is used by storage vendors to develop their solution in relation with vSphere.
Check the FAZ section and see http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2004098
http://www.vmware.com/products/datacenter-virtualization/vsphere/storage-api.html