After I installed the asa5510 with failover feature, I found that the ftp/netbios download traffic on primary unit was about 1.2Mb, so I forced the secondary unit to takeover these traffic instead of primary unit, I found that the throughtput was about 50Mb, Please anyone help me to identify this problem.
1. Outside and inside interfaces don't have any error.
2. When connect PC directly to ASA on outside and inside interface and testing download via ftp/netbios, the problem still occured.