F5 and a pool of webservers - what settings/algorithm to use

Hi sriramgd,

 

 

Your situation is tricky. The most that I can give you since I am not aware of your exact circumstances is a suggestion to alter your configuration.

 

 

First, if you are using IIS then the thread counts should be directly tied the application pool being utilized by the website (on that configuration). If you say have 2 servers, I would suggest "duplicating" the website on the same server with a different application pool being used for the second instance of the website (you should be able to reference the same code that the original website is utilizing to decrease the administrative overhead for altering your configuration). Then add the duplicate websites into the pool to effectively double the number of pool members.

 

 

Website.Server.Pool:

 

10.10.10.10:80 - Server 1 - Original Website

 

10.10.10.10:81 - Server 1 - Duplicate Website

 

20.20.20.20:80 - Server 2 - Original Website

 

20.20.20.20:81 - Server 2 - Duplicate Website

 

 

Then use Priority Activation Groups to separate the Originals from the Duplicates:

 

 

Website.Server.Pool:

 

10.10.10.10:80 - Server 1 - Original Website - Priority Activation Group 2

 

20.20.20.20:80 - Server 2 - Original Website - Priority Activation Group 2

 

10.10.10.10:81 - Server 1 - Duplicate Website - Priority Activation Group 1

 

20.20.20.20:81 - Server 2 - Duplicate Website - Priority Activation Group 1

 

 

Note: Higher the Activation Group Number the higher the preference.

 

 

Then set the Priority Activation Group setting to "Less than...." "2" Members Available. This will make sure that 2 of the 4 are always available.

 

 

Then set your connection Limit to a recoverable limit for your servers.

 

 

Website.Server.Pool:

 

10.10.10.10:80 - Server 1 - Original Website - Priority Activation Group 2 - Connection Limit 100?

 

20.20.20.20:80 - Server 2 - Original Website - Priority Activation Group 2 - Connection Limit 100?

 

10.10.10.10:81 - Server 1 - Duplicate Website - Priority Activation Group 1 - Connection Limit 100?

 

20.20.20.20:81 - Server 2 - Duplicate Website - Priority Activation Group 1 - Connection Limit 100?

 

 

If they reach that limit they will be "removed from service" and one of the duplicates will become available to keep the application available (without overloading them). As soon as they process enough to fall below the connection limit the original websites would be come available again and the duplicates would go back into a standby mode (after they finished processing what they had sent to them during the overflow).

 

 

This is just a suggestion that you will need to test and tweak to fit your situation, but I think it might help you resolve your overload issue.

 

 

Hope this helps.