Ratio member lb method

When determining which pool member to load balance a connection to, the first thing the BIG-IP system does is determine which pool members are available to choose from. One of the things that it takes into consideration is Priority Group Activation. You have two pool members in the pool, and each is in a separate priority group. With activation set to "Less than 1 member" that means only 1 member needs to be available to make a load balancing decision. Furthermore, it means all connections will be load balanced to that one pool member unless that pool member becomes unavailable. In other words, the load balancing method (ratio) is irrelevant as the BIG-IP system needs only 1 pool member available to make a load balancing decision.

There are a variety of reasons why a pool member may become unavailable, including hitting a connection limit or a monitor marking the pool member or node down. If either of those conditions occurs, and the minimum 1 pool member is no longer available, the BIG-IP system will activate whatever members are in the next lower priority group, and include those members in load balancing until the higher priority group member is once again available. If, for example, you hit a connection limit on node1, node2 would be activated and receive connections until such time as node1 was no longer at its limit.

Priority Group Activation is generally configured only if you need or want to hold some pool members in reserve to handle certain traffic situations, such as unexpected volume or perhaps a maintenance requirement. Since you only have two pool members, if you want traffic to always load balance between the two according to your static ratio, then you might disable Priority Group Activation. If you do want most traffic to go to node1 and use node2 only when node1 is not available, then leave Priority Group Activation set as you have, but understand that the load balancing method is effectively rendered moot as there will only ever be one member "active" at any time (as far as Priority Group Activation goes).