Two-way mirroring requires a rbd-mirror daemon running on both clusters, the primary and the secondary. With two way mirroring it is possible to mirror data or images from the primary site to a secondary site, and the secondary site can mirror data or images back to the primary site. 

We will not be demoing this configuration in this book at it is very similar to the one-way configuration, but we will highlight the changes needed for two way replication at the pool level, these steps are covered in the one-way replication recipe.