Distributed Data Storage Assume relational data model Replication System maintains multiple copies of data,stored in different sites, for faster retrieval and fault tolerance. Fragmentation Relation is partitioned into several fragments stored in distinct sites Replication and fragmentation can be combined Relation is partitioned into several fragments:system maintains several identical replicas of each such fragment. Database System Concepts-5th Edition,Aug 22,2005. 22.5 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 5 22.5 ©Silberschatz, Korth and Sudarshan th Edition, Aug 22, 2005. Distributed Data Storage Assume relational data model Replication System maintains multiple copies of data, stored in different sites, for faster retrieval and fault tolerance. Fragmentation Relation is partitioned into several fragments stored in distinct sites Replication and fragmentation can be combined Relation is partitioned into several fragments: system maintains several identical replicas of each such fragment