Table 3-18 Data Replication options Suitable Distance Method Replication by database server Replication by storage Data to be Replicated Performance Impact Data Loss Evaluation Asynchronous Any distance Business data stored in database Small In-flight data could be lost ◎ Synchronous Less than 100 km Business data stored in database Large (Application has to wait for confirmation of data write to DR site) No data loss △ Asynchronous Any distance Both business and system data in selected storage volumes Small In-flight data could be lost ○ Synchronous Less than 100 km Both business and system data in selected storage volumes Large (Application has to wait for confirmation of data write to DR site) No data loss △ Any distance Both business and system data No impact Can be huge depending on the frequency and timing of transporting backup data × Send backup data to remote location periodically Source: Preparatory Survey Team Reasons for adopting this replication by database server are as follows:  No limitation of distance  Near-zero data loss  Smaller performance impact  Only business data needs to be replicated (System data will be replicated only when changes are applied to production environment.)  For CBM-NET Phase 2 environment, cost of replication by database server’s function can reduce the cost more than replication by storage function. The following figure shows the data replication (asynchronous replication by database). 63