Which replication type requires data written to the primary site first before being synced to a remote site?

The correct answer is synchronous replication. This replication method ensures that any data written to the primary site is immediately replicated to the remote site as part of the same transaction before the transaction is considered complete. This approach guarantees data consistency, as both sites have the same up-to-date data at all times. It is particularly beneficial in environments where data integrity is critical, such as in financial transactions or any scenario where real-time data accuracy is essential.

Synchronous replication is distinct from asynchronous replication, where data written to the primary site is acknowledged before it is sent to the remote site, leading to a potential delay in data consistency. While mirroring and volume sync might incorporate some aspects of replication, they do not necessarily enforce the requirement that writes at the primary site must complete before syncing to a remote location like synchronous replication does.