Load Balancing Application & Database Servers

Q1 I am not sure you can do what you are asking but i may be interpreting the question incorrectly, have a read of "Specifying the load balancing method" Unless you write is in an iRule

 

http://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm_configuration_guide_10_0_0/ltm_pools.html1215305

 

 

If they where 4 separate webserver as VIPS and you had a GTM then you would set the last resort pool and if the true pool (server) is down then it would use servers listed. IF you GTM you may be able to do the same with an irule, have your normal VIP setup but also have an irule so that if the pool goes down it select another pool.

 

 

Q2 I think you will fall into the scenario again where you will ned to use an iRule. By nature prioirty group will pick the higher prioty. You could write an irule to LB based and set priority but if the pool goes down change the priority and that way the the active will always stay highest.