LVS TCP connection timeouts - lingering connections
Solution 1:
Do you have persistent connection enabled? The persistent connection timeout can be set using -p [timeout]
This keeps connection b active to route further requests from the client IP to the same real server.
Solution 2:
You can use the --set command to decrease the timeout.
/sbin/ipvsadm --set 3600 120 300
Or give haproxy a try.