Where in the World is My Data?
Users of websites such as Facebook, Ebay and Yahoo! demand fast response times, and these sites replicate data across globally distributed datacenters to achieve this. However, it is not necessary to replicate all data to all locations: if a European user's record is never accessed in Asia, it does not make sense to pay the bandwidth and disk costs to maintain an Asian replica. In this paper, the authors describe mechanisms for selectively replicating large-scale web databases on a record-by-record basis. They introduce a flexible constraint language to specify replication policy constraints.