Cisco introduce OTV as solution to give two physical separate Data centers l2 connectivity over common L3 network , so why we need that if we have L2 VPN solution ? and what is the benefits of implementing OTV and excluse L2 VPN ?
Here is a short answer:
OTV allows for more than just two sites. It prevents bridging loops better than spanning tree.
OTV controls unknown MAC flooding, and only advertises MACs to other sites as necessary.
OTV limits "local" protocols like STP, VTP, etc to the local site.
OTV prevents broadcast storms, L2 loops, etc from affecting more than one location. With a L2 VPN, all can be affected.
OTV runs over IP. You can use it where you can't get a L2VPN.