Some tips on load balancing on ASA:
With Active/Active failover, both units can pass network traffic. This lets you configure load balancing on your network. Active/Active failover is only available on units running in multiple context mode. To provide load balancing, use Active/Active failover. If you do not want to provide load balancing, use Active/Standby or Active/Active failover
The security appliance does not provide load balancing services. Load balancing must be handled by a router passing traffic to the security appliance.
For load balancing configurations, you should assign each failover group a different unit preference
For more information see the link below:
http://www.cisco.com/univercd/cc/td/doc/product/multisec/asa_sw/v_7_1/conf_gd/failover.htm
