I need to investigate the use of HAProxy in our system. We have a main server running some service (kind of a proxy) that speaks to other servers, each running a different service at a layer lower. These services on the lower layer might need to speak so others on this layer. We want to put HAProxy in front of the main server, but we also need the servers/services on the lower layer to benefit from being HA. Is this possible, and/or common?