Load balancing imbalance in ACE

Question

We are facing slowness an http application which is due to connection imbalance. This setup has one set of Load balancer and a proxy in DMZ where the connections gets terminated from the users and a load balancer inside LAN which load balances between the end point servers. All user connections terminate on the DMZ load balancer / proxy and proxy connects back to the internal load balancer VIP. (By collating a number of connections to very few - default proxy behavior) . Internal load balancer VIP does load balancing based on the number of connections in a least loaded manner and this load balancer doesn’t see how many sessions are beneath each connections and it distributes each connection to server underneath. Thus if one connection has around 100 sessions, another may have only a few and each of this gets forwarded to the end server causing the imbalance.
Is there a way that this imbalance can be tackled in this setup.
Users --> Proxy ---> Load balancer (Cisco ACE) --> Server 1
                                                                                                Server 2
                                                                                                Server 3
Least Connections predictor
HTTP Cookie insert sticky

Answer 1

Hi,
Persistance rebalance should solve the issue for you.
The persistent-rebalance function is required if you have proxy users and the proxy shares one TCP connection between multiple users.
With this behavior, inside a single connection you will see different cookies. Therefore, for each cookie, ACE needs to first detect the new cookie and then loadbalance to the appropriate server.
this is from the admin Guide :
The following example specifies the parameter-map type http command to enable HTTP persistence after it has been disabled:
host1/Admin(config)# parameter-map type http http_parameter_map
Host1/Admin(config-parammap-http)# persistence-rebalance
Please refer the following link for more info :
http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/ace/vA4_2_0/configuration/slb/guide/classlb.html#wp1062907
hope that helps,
Ajay Kumar