What is the compression algorithm used by vSphere Replication to compress data at the source?

FastLZ is the specific compression algorithm vSphere Replication employs when source-side compression is enabled on a replication job. It is a lightweight, block-based LZ-family algorithm optimized for speed, making it appropriate for real-time data stream compression during replication without imposing heavy CPU overhead on the source host. Enabling this option reduces the amount of data transmitted over the network to the target site.

Lz4 is a popular high-speed compression algorithm used in other VMware products such as vSAN, but it is not the algorithm used by vSphere Replication.

Lzr is not a recognized compression algorithm used in vSphere Replication source compression.

Lzx is a compression format associated with Microsoft Cabinet files, not with vSphere Replication.