chore(docs): clarify large cluster docs
@@ -5,11 +5,12 @@ Starting from acs-engine v0.3.0, acs-engine supports using exponential cloud bac
## To Use
Declare your kubernetes cluster API model config as you normally would, with the following requirements:
-- Make sure you're declaring version 1.6.6 of Kubernetes (the only currently supported version that includes the configuration vectors described in [examples/largeclusters/kubernetes.json](https://github.com/Azure/acs-engine/blob/master/examples/largeclusters/kubernetes.json)). Kubernetes v1.6.6 is the default Kubernetes version starting in acs-engine v0.3.0.
+- You must be using at minimum the `v1.6.6` version of Kubernetes to have access to the `kubernetesConfig` configuration vectors exemplified in [examples/largeclusters/kubernetes.json](https://github.com/Azure/acs-engine/blob/master/examples/largeclusters/kubernetes.json). As long as you are using a version of acs-engine `v0.3.0` or newer, your kubernetes cluster specification will fulfill this minimum version requirement.
- We recommend the use of smaller pools (e.g., count of 20) over larger pools (e.g., count of 100); produce your desired total node count with lots of pools, as opposed to as few as possible.
- We also recommend using large vmSize configurations to reduce node counts, where appropriate. Make sure you have a defensible infrastructure justification for more nodes in terms of node count (for example as of kubernetes 1.7 there is a 100 pods per node limit), instead of opting to use more powerful nodes. Doing so reduces cluster complexity, and azure resource administrative overhead. As Kubernetes excels in binpacking pods onto available instances, vertically scaling VM sizes (more CPU/RAM) is a better approach for expanding cluster capacity, if you are not approaching the pod-per-node limit.
## Backoff configuration options
+The following configuration parameters are available in the `properties.orchestratorProfile.kubernetesConfig` configuration object in the api model specification:
```json
"cloudProviderBackoff": {
@@ -49,3 +50,4 @@ Declare your kubernetes cluster API model config as you normally would, with the
"value": "1m" // how often kubelet posts node status to master
}
```
+The [examples/largeclusters/kubernetes.json](https://github.com/Azure/acs-engine/blob/master/examples/largeclusters/kubernetes.json) api model example suggests how you might opt into these large cluster features following the guidelines above.
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