Load balancing one-arm and two-arm modes

Question

I searched the internet for a clear explanation of how these 2 type of load balancing methods exactly work, what are the benefits/issues that come with each and so on, but I could find a clear resource on which to read what I am asking.

Would you be able to explain to me in a clear manner what are these 2 mods, when to prefer one or the other, the trade-offs, ecc? If you have an online resource or a book, please point it out.

Solution

"Arms" kinda nebulously reference to the number of network connections the load balancing appliance has. Note that arms refers to logical connections, so bound nics would still be only one connection despite being multiple cables.

in two-arm, the LBA acts as a bridge between two network segments, so it is In-Line between the clients and the servers.

One-Arm has a single network connection to a lan, upon which the servers, and perhaps even the clients reside on. Instead of using direct physical connections to the servers, it uses NAT tricks to virtual route the traffic between clients and servers through the LBA, even though they are all on the same network.

see a description with diagrams here: http://networkgeekstuff.com/networking/basic-load-balancer-scenarios-explained/