What is the primary difference between synchronous and asynchronous replication?

The primary difference between synchronous and asynchronous replication lies in how data consistency is handled during the replication process. Synchronous replication ensures that data is written to both the primary and secondary storage systems simultaneously. This means that both locations hold identical data at the same time, achieving real-time data consistency. This method is critical in scenarios where it is vital for data integrity and continuity to have the most current information available instantly across multiple locations.

In contrast, asynchronous replication does not require the primary and secondary systems to be updated simultaneously. Instead, there may be a time lag during which data is first written to the primary site and later transmitted to the secondary site. This delay can improve performance, as it allows the primary system to continue operating without waiting for confirmation from the secondary location. While asynchronous replication can still maintain a certain level of data integrity, it does not achieve the immediate consistency that synchronous replication guarantees.

By focusing on real-time updates, synchronous replication provides stronger data protection for mission-critical applications, which is the key aspect distinguishing it from asynchronous methods.