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Need help to understand Dynamic Ratio Load Balancing.

swo0sh_gt_13163
Nimbostratus
Nimbostratus

Hi folks,

 

I am new to F5 and recently attended an LTM training. However I am bit confused about dynamic load balancing method i.e. Dynamic Ratio.

 

I have tried following SOL9125 document, however it didn't help. Could anyone please spend a moment to explain it?

 

Cheers! Darshan

 

6 REPLIES 6

afedden_1985
Cirrus
Cirrus

I'm checking on this but it sounds like you can use the ratio field with Round Robin as explained in SOL11870 and accomplish the same goal of weighting servers without the CPU overhead that comes with using Ratio (Member) mentioned in SOL9125.

 

nitass
F5 Employee
F5 Employee

I have tried following SOL9125 document, however it didn't help.

 

what does it not work?

 

swo0sh_gt_13163
Nimbostratus
Nimbostratus

Hi Nitass,

 

I couldn't understand the concept explained in document SOL9125. So I was looking for some help to simplify the concept.

 

Darshan,

 

nathe
Cirrocumulus
Cirrocumulus

Darshan, I've not had a reason to use a dynamic load balancing method myself but here is what I understand. With normal Ratio method you manually specify a weight to each pool member so then the load balancing of connections to these members is weighted accordingly. You would use this if one or more of the pool members were servers with a better or worse specification than the others, for example. As for Dynamic Ratio, it's exactly the same but the weighting of pool members is dynamic and is constantly changing. This can be set as a reflection of memory or CPU usage on the pool member, relative to the other pool members. Hope this helps in some way. N

 

Kevin_Stewart
F5 Employee
F5 Employee

Ratio load balancing is a way of manipulating the load balancing decision based on some weighted value, and is most often used when the server resources are not all the same (different CPU and memory capacities). There are basically two kinds of ratio load balancing:

 

(Regular) Ratio balancing - this is where you assign a static ratio number to a node or pool member. Example:

 

Node 10.10.10.10 Ratio 1 Node 10.10.10.11 Ratio 2 Node 10.10.10.12 Ratio 2 Node 10.10.10.13 Ratio 3

In this example we're literally saying something like for every 1 connection sent to node 1, send 2 new connections to nodes 2 and 3. It's not really that simple, but hopefully you get the idea.

 

Dynamic Ratio balancing - this has the same effect as above, but uses ratio values derived from calculations instead of the arbitrarily assigned numbers. You must apply an SNMP_DCA or SNMP_DCA_BASE monitor to the pool (or nodes) and customize the threshold values. The SNMP data received from the servers using this monitor is used to assign dynamic ratio values for the load balancing decision.

 

Again, the primary use case for any ratio load balancing is when you have pool members of varying size/capacity.

 

swo0sh_gt_13163
Nimbostratus
Nimbostratus

Hi Kevin/all,

 

Thank you very much for detailed explanation about the Dynamic Ratio Load-balancing. This is pretty helpful and I am absolutely clear with the concept.

 

Appreciate your all efforts and time you'd spent on this post. Thank you very much again!

 

Regards, Darshan