Failover and Failback between pools using % availability
We are migrating from Cisco ACE to f5 Load balancer. We have configuration in ACE - there is primary pool(4 members) and backup pool(2 members). In ACE: partial-threshold 49 back-inservice 99 Above command on the CISCO ACE will be send all traffic to the primary pool and in an event when there is less than 3 servers available on primary pool i.e., less than 49% availability the traffic will switch to the backup pool. Traffic will failback to the primary pool only when there is more than 99% availability on the primary pool. i.e., all the members are avaiable. Is it possible to achieve this scenario using iRULE and by calculating the % availablility on the pools to trigger failover and failback?