CSS Weighted Round Robin service weight

[tcyee]

I have been asked to balance 3 servers with only 10% of traffic going to one and the rest going to the other two. What weights do I assign each of the 3 services to achieve this percentage? I can't find any information or documentation that goes into detail on how the math works for the weights.  This is on a CSS 11500.

[rodrguti_2]

Hi,

In order to calculate the weight that we can use on the service this is the way you can do it:

We can assign a weight from 0 to 10, where 0 means that the service wont take any
connection, and 10 the service will take all the traffic, by default all services has a
weight of 1.

What you can do is this:

You have 4 servers, I am going to assign a weight of 3 and 2:

ServiceA: weight 3
ServiceB: weight 3
ServiceC: weight 3
ServiceD: weight 2

Now, how do I know which weight I can use?, in order to know this please check this:

1) 3+3+3+2 = 11

2) 100 (represent the 100% of the traffic) / 11 = 9.09 (for each service)

3) serverA: 9.09 * 3 = will take 27.27 % of the 100% of the traffic
   serverB: 9.09 * 3 = will take 27.27 % of the 100% of the traffic
   serverC: 9.09 * 3 = will take 27.27 % of the 100% of the traffic
   serverD: 9.09 * 2 = will take 18.18 % of the 100% of the traffic

So, server D, will take less connections than the other 3 servers about 9.09% less.

If you add a 5th server it will be the same, the formula will be the same, also you can
use different weights for each server, but you want to make sure the percentage that each
server will take.

Hope this help.

Rodrigo