When using the default stream settings, the latency from reading the data in the source to streaming it into the destination is between 10 and 120 seconds.
Kerf2 is designed for full concurrency. It also adds transparent type promotion, a C++ instead of C basis, and more.
Which goes unlicensed right now and was created just a bit before the license change in Kerf1. I wonder if Kerf1 will get any more attention or the focus is now at Kerf2.
Google open sourced vitess for scaling out and coordinating (sharding + replication, schema rollouts) mysql databases, it seems they use it internally: http://code.google.com/p/vitess/