Yes, we are using multi-tenant SDN plugin and our nodes are 8cpu x 64 GB 
capacity.  Planning to host more than 100 pods per node. With the latest 
OpenShift release, I hope we don’t have old hard limits on cluster size and # 
pods on per node

I don’t have an accurate answer for # services per project, which we can’t 
control at platform side.

Based on abov facts can you recommend a decent CIDR for pods & service?

--
Srinivas Kotaru

From: "[email protected]" <[email protected]>
Date: Thursday, October 6, 2016 at 1:50 PM
To: Srinivas Naga Kotaru <[email protected]>
Cc: dev <[email protected]>
Subject: Re: NetworkCIDR for big cluster



On Oct 6, 2016, at 1:23 PM, Srinivas Naga Kotaru (skotaru) 
<[email protected]<mailto:[email protected]>> wrote:
Hi

We ‘re building 3 big clusters, 1 specific to each data center. growth  
expected to 1000 nodes each cluster over the time.

Questions:


1.
# egrep 'clusterNetworkCIDR|serviceNetworkCIDR' 
/etc/origin/master/master-config.yaml

  clusterNetworkCIDR: 10.1.0.0/16<http://10.1.0.0/16>
  serviceNetworkCIDR: 172.30.0.0/16<http://172.30.0.0/16>

above are default subnet values.  These defaults will be sufficient for 1k 
clsuter size?

That would be 64k pods and services.  If you expect densities in excess of 100 
pods per node you should probably plan for a larger cidr for the cluster 
network and if you are using the multi tenant plugin you'll also want to plan 
around how many unique projects you will have.

So inputs are:
# of projects
Expected number of services per project (simple apps or complex apps per 
project)
Expected pod densities per node




2.      if answer is ‘no’ can we change once cluster is build with new CIDR 
values depending on growth? ( I heard it is not possible once cluster was build)


It is possible to grow it if you include the original cidr in the expanded 
cidr.  However, it can be disruptive so we recommend planning up front.  I 
would recommend leaving the possibility of a larger block open by expanding the 
mask if you are unsure about exact limits.



3.      if answer is ‘no’ what is the right CIDR’s for 1k cluster size?


--
Srinivas Kotaru
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