Which of the following data replication technologies has the GREATEST impact on an application's I/O performance to the source data?

Synchronous replication guarantees zero data loss by requiring the write operation to be successfully committed to both the primary storage and the remote replica storage before the I/O is acknowledged back to the application. This mandatory waiting period directly adds latency to every write operation at the source, thus having the greatest impact on the application's I/O performance.

ISL trunking is a networking feature used in Fibre Channel SANs to aggregate multiple links between switches for increased bandwidth and redundancy, not a data replication technology that dictates I/O performance impact.

Semi-synchronous replication, while having some impact, generally acknowledges the write sooner than full synchronous replication (e.g., once received by the target), resulting in less latency than true synchronous.

Asynchronous replication has the least impact on source I/O performance because the primary storage acknowledges the write immediately, and data is replicated to the target independently in the background.