Forum Discussion
gc_33734
Nimbostratus
NimbostratusRatio load balancing syntax
I am not so sure this is an "advanced" question, but I was unable to find this answered specifically enough anywhere else.
I am using an f5
version: BIG-IP 9.4.3 Build 1.4 Final
I am in a situation where I need to use the console/command line interface to configure my load balancer. I have a user that wants a pool set up with 2 devices, load balanced with a weighted ratio of 75%-25%. I need to know the syntax for creating a pool with 2 members, one which will receive 75% of incoming connections, with the other member receiving 25%. Here is what I used to configure the BIGIP the way it is right now:
node 10.10.145.10 {
ratio 75
}
node 10.10.145.11 {
ratio 25
}
pool TestPool_10049 {
lb method member ratio
member 10.10.145.10:10049 ratio 75
member 10.10.145.11:10049 ratio 25
}
virtual TestPool_10049 {
destination 10.193.64.222:10049
pool TestPool_10049
}
If I am in the console/command line interface and I do a "show" on this pool I get:
POOL TestPool_10049 LB METHOD member ratio MIN/CUR ACTIVE MEMBERS: 0/0
| conns (cur, max, limit, tot) = (0, 2, 0, 10)
| (pkts,bits) in = (55, 28320), out = (50, 29040)
+-> POOL MEMBER TestPool_10049/10.10.145.10:10049 ACTIVE,UNCHECKED SESSIONS ENABLED
| | priority 1 ratio 75 dynamic ratio 1
| | conns (cur, max, limit, tot) = (0, 1, 0, 5)
| | (pkts,bits) in = (28, 14416), out = (25, 14520)
| | requests (total) = 5
+-> POOL MEMBER TestPool_10049/10.10.145.11:10049 ACTIVE,UNCHECKED SESSIONS ENABLED
| priority 1 ratio 25 dynamic ratio 1
| conns (cur, max, limit, tot) = (0, 1, 0, 5)
| (pkts,bits) in = (27, 13904), out = (25, 14520)
| requests (total) = 5
So I must be doing something wrong, since the connections are being sent 50/50 to each member of the pool. Please help me out, and remember that I only have the console/command line interface right now.
Thanks
- JRahm
Admin
Ratio works by distributing the connections round-robin to the pool members until the configured level is exceeded. In your case, you won't meet your desired goal of 75/25 until 100 connections. The ratio is a representation of connections, not percentage, so I would suggest changing your ratio from 75/25 to 3/1. 
gc_33734Hey thank you very much, it is working correctly now. I set the ratio to 3:1 for both the members of the pool, and the nodes. Is it required that I set both of these for it to work? Either way, I appreciate the fast help - thank you very much!
node 10.10.145.10 {
ratio 3
}
node 10.10.145.11 {
}
pool TestPool_10049 {
lb method member ratio
member 10.10.145.10:10049 ratio 3
member 10.10.145.11:10049
}
So do I have to set both the "node" ratio and the "member" ratio? Just curious, the pool is functioning as desired right now.- JRahmThat depends on the algorithm you selected, ratio(node) or ratio(member)? Typically, if the node (read, IP address) only has one service, I use member. But if I have several services running on each node, then I will use node load balancing. That way, regardless of what's happening within an applications distribution, the physical servers aren't out of balance.
A very notable exception to this setup would be batch applications. Anything less than iControl integration with batch apps is a very slippery slope. 
adamcox_1480I'm attempting to run the same setup but on a larger scale. I want to roll out a new application to a select % of people slowly ramping up the percentages. I have four boxes of version 1.0 and two boxes version 2. In order to setup a 5% to version 2 boxes I'm thinking
v1 ratio 100
v1 ratio 100
v1 ratio 100
v1 ratio 100
v2 ratio 2
v2 ratio 2
The reason I came up with 2 is that I found the total of my main load server (400) then found 5% of that(4). The distributed that 5%(4) across the two boxes with a ratio of (2)
ie sum(v1)*.05/count(v2boxes). The logic seems sound, if I'm on the right track.
The thing that concerns me is when I want to get up to 50% it ends up all being 100. This doesn't seem right to be because that would evenly distribute across all boxes. Where I want 50% load split across v1 and 50% across v2.
So my guess would be (but breaks my formula)
v1 ratio 100
v1 ratio 100
v1 ratio 100
v1 ratio 100
v2 ratio 200
v2 ratio 200
I speculate that I shouldn't be dividing up the total across boxes, but using that same total for each box (if that makes sense)
Thanks for any advise or point me to some documentation. I have 8 pools with different server distributions of v1/v2 servers to apply this too.
EDIT: As a follow up, i'm going to be using a 45day cookie persistance to maintain "once on a version stay on a version"
HamishCirrocumulus
Not sure about your logic there for working out 5% of 400... The result should be closer to 22 (Once you added in the 2x 20's to get 440 for the total, 5% of that is 22), just as a quick does it feel right kind of check...
As you surmise about the 50% ration, to get 50% you'd need the total of all the V1's to equal the total of all the V2's. And your guess is correct 4x100 = 2x 200)... And the reason it breaks your formula, is because your formula is wrong...
H- adamcox_1480ok, so another way to approach it would be start with a grand total, lets say 100. Then divide that up to the appropriate percentages.
scenario:
- define pool ratio total of 100
- six servers in pool
- divide the total pool ratio among the servers into two groups
- 4x24 and 2x2 = 100 (96/4)
- 4x12 and 2x26 = 100 (48/52) almost 50/50
- 4x13 and 2x26 = 104 (50/50) goes over but is going to be evenly distributed
- 4x1 and 2x2 = 8 (50/50) this would do the same as previous just in fewer requests
Would it be safe to say:
Members of the same weight are LB Round-Robin once the ratio weight determines which member group is going to get the request. - HamishI didn't think that was the way the algorithm went... (i.e. two steps). But then the actual implementation is going to be secret anyway...
Disclaimer: Most of my ratio work has been with dynamic ratios...
H 
hoolioCirrostratus
I think it should be round robin between members of the same ratio. You could test this by using ratio load balancing with each pool member set to a ratio of 1. Note that this isn't a recommended config for doing ratio as there is more overhead with ratio (even with even ratios) than using round robin.
Aaron- adamcox_1480Thank you all for your help. I'm trying to roll out this next version and being able to do it in a % ramp up process to be able to tune and tweak. I figured my options were two pools or ratio weights.
I was able verify the appropriate distribution between two members with a 1000 curl calls. But when it came to weight distributing within a pool with 6 members the exact implementation of the ratios got me. The part that was counter intuitive was setting the weight of the boxes that I want more traffic to to a lower weight (because there are more boxes). From Hamish's comment.
I'll keep tweeking and testing. Thanks again.
