is a term used in IBM
storage systems, to describe a group of services that provide a method of copying or moving data from one location to another.
Generally a source and target logical disk are required. Data is copied or moved form the source to the target. The method by which data is moved or copied depends on the service being used:
- Replication services provide methods of creating consistent copies of a source or group of source logical disks. This is generally used for business continuity by replicating business critical systems from one site to another.
- Synchronous replication services result in the target being in perfect synchronization with the source (source data writes are not completed until the target has also returned completion. Only applicable to relatively short distances (<500km) due to the latency introduced to the source operations.
- Asynchronous replication services result in the target being some period of time (usually a few seconds) behind the source, as source writes are completed before the target write has been completed. Applicable to relatively large distances (>500km to many 1000's of km)
- Snapshot services provide methods of creating a point in time copy of a source logical disk. This is generally used to either archive (backup to tape) or create a copy of a source logical disk to perform application development.
- Data migration services provide methods of moving data from one physical disk to another, while maintaining logical disk access, and thus application access while the data is in the act of moving.