A financial institution requires a disaster recovery solution for its primary online transaction processing (OLTP) database. A key requirement is to ensure zero data loss (RPO of zero) in case of a site failure. The solution must guarantee that a transaction is written to both the primary and the secondary data centers before it is considered complete. Which of the following replication methods BEST meets this requirement?
The correct answer is synchronous replication. This method writes data to both the primary and secondary storage locations at the same time. A write I/O operation is not considered complete until an acknowledgment is received from both the primary and secondary sites. This ensures that the data at both sites is identical, which achieves a Recovery Point Objective (RPO) of zero, meaning no data is lost during a failover. This is critical for transactional systems where data integrity is paramount.
Asynchronous replication is incorrect because it writes data to the primary storage first and then copies it to the secondary site after a delay. This creates a non-zero RPO, as some data may not have been replicated at the time of a failure.
Snapshot replication is incorrect as it captures the state of data at specific points in time. This method is suitable for less critical systems where some data loss between snapshots is acceptable, but it does not meet the zero RPO requirement for a critical OLTP database.
Bidirectional replication describes a topology where two sites can send and receive replicated data, allowing either to act as the primary. While useful for active-active scenarios, it describes the direction of data flow, not the timing mechanism that guarantees zero data loss. Bidirectional replication can be implemented either synchronously or asynchronously, but synchronous replication is the specific method that meets the zero RPO requirement.