[Users] migration of VM, which protocol actually works?

i wanted to learn about the modules so that i could understand how the engine POSTS and sends data to the backend sql database and other scripts to perform various options. for e.g i need to know which code actually collects the storage path for the ISO s during ISCSI storage domain setup. also how the hosts, clusters and data centers are made and stored at the backend. if i want to add a new UI that bypasses some of these complicated tasks (again for personal understanding), will I be able to do that. Also i would like to mention that am working on making a little changes to how the ISCSI protocol works.. My another doubt is: when are the NFS/ISCSI/FC protocols actually used in ovirt. like what part of the VM running state? are their purpose limited to just copying the ISO from the storage center to the path required by the Host. Are the protocols them self responsible for sending and getting data during VM execution on a node. The concept of node and migration has left me a little confused. since each node can run multiple VMs , so during the running/execution of the VM , do the network protocols actully work, if not , then how is that achieved. if yes, again my question arises, which module should i focus on regarding this issue. thanks -- -Aditya Mamidwar