How are you determining that load is not evenly distributed? Are you comparing number of requestors in the SMA? What is the load distribution logic used by F5? Round-robin, weighted round robin, current load?

If you compare number of requestors in the SMA and the actual distribution statistics from F5, there's always a perceived imbalance.

1. Due to server affinity the same user who is logged into one server will have all requests sent back to the same server.

2.  If the distribution logic depends on current load (remember http requests are single request/responses connections not open connections that last the duration of the user session) then its quite possible for F5 to determine that one server (the one that has more logged in users) to be less heavily loaded, simply because those users aren't hitting the server as actively as the one with fewer logged in users.

3. Requestors in the SMA are not passivated for 1 or 2 hours. Which means that the number of requestors reported in the SMA could be requestors which haven't seen any user activity for a while(check last access time) but haven't reached the passivation threshold.

I would monitor this (gather statistics) over a period of time before concluding if there's a problem.

Regards

Patrick

Hi Patrick -  Thank you for your detailed response!

Please find the answers to your questions as follows:

How are you determining that load is not evenly distributed? Are you comparing number of requestors in the SMA?==>>Using SMA by looking at requestor count on each nodes and also by looking at hourly log-usage report.

What is the load distribution logic used by F5? Round-robin, weighted round robin, current load?==>>Load balancing method is set as "Observed Member"

we have 15 minutes of timeout period after which requestors get logged off if inactive for more than 15 minutes. Sometime we notice that one node has 20+ users while other node doesn even have 1 user. We are trying to look at log usage statistics for few days to get to know the root cause.

Tried investigating more but could not find any particular root cause as of now. If someone else has experienced the same then please share your findings.

Have you tried other load balancing options?

For example, "Least Sessions"

Thank you Chunzhi_Hong I will try to contact my LTM team and see what it takes to change the load balancing method to Least Sessions.