Abstract: In this 45 minute talk, I go over the differences between how rsync and ZFS filesystem replication work, and what the performance implications are --including demonstrating a real-world use case where ZFS replication is more than 1,000x faster than rsync. The talk mentions my replication tool Syncoid, which makes the actual practice of ZFS replication much, much easier, but focuses more on the bare nuts and bolts of replication itself.