[mistwang]

Please check WAITQUE_DEPTH of phpLsapi during a taffic surge, if it is very high, you need to improve you PHP/MySQL code, as it is not able to keep up with the traffic. You can try raising "Max connection" of phpLsapi, but it may not help much.

You can also looking into our Anti-DoS configuration: http://www.litespeedtech.com/how-tos.html#qa_dos