1. A geographically distributed storage system for managing the distribution of a plurality of data elements as a global database coherently distributed over a plurality of sites, comprising: a plurality of geographically distributed sites, each comprising a site storage unit configured for locally storing a portion of said globally coherent distributed database comprising the plurality of data elements, such that respectively stored portions form said global database and a local access point configured for receiving requests relating to any of the plurality of data elements wherever located on said distributed global database; and a data management module configured for forwarding requested data elements from respective portions of said global database at which said requested elements are stored to the local access point, said forwarding of said element being to a requesting one of said plurality of geographically distributed sites, from which said request from said access point is received, and storing said at least one requested data element at said requesting site, thereby to provide local accessibility to any given data element for future requests from said requesting site when a same element is requested a second time, while maintaining the global coherency of said globally coherent distributed database, wherein each said site storage unit comprises a global storage device of a dynamic storage sub-system, said dynamic storage sub-system being configured for storing at least a unified database comprising a replica of each said data element, and wherein each said data element comprises a tag indicative of one of said storage sub-systems, an access right to each said data element is exclusively granted to a respectively indicated sub-system.