Hi, 
I went through ceph open-source code (link: https://github.com/ceph/ceph) and saw your contribution. It would be of great help if you answer some of the questions.  

Following are some queries:
1. Wanted to know the exact connection in ceph? Is it using iscsi protocol to transfer RBD block devices to clients? 
2. How do OSDs join forces to create a single rbd block?
3. Do you know the precise protocol that is used to send rbd images to clients?

Hoping to hear from you soon. 

Thanks and regards,
David Thomas