Update controlplane.md

content/reliability/docs/controlplane.md

@@ -66,6 +66,9 @@ The following Prometheus query can be used to monitor the current size of etcd.
 max(etcd_db_total_size_in_bytes{job="kube-apiserver"} / (8 * 1024 * 1024 * 1024))
 ```
 
+!!! attention
+    When the database size limit is exceeded, etcd emits a no space alarm and stops taking further write requests. In other words, the cluster becomes read-only, and all requests to mutate objects such as creating new pods, scaling deployments, etc., will be rejected by the cluster’s API server.
+
 ## Cluster Authentication
 
 EKS currently supports two types of authentication: [bearer/service account tokens](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#service-account-tokens) and IAM authentication which uses [webhook token authentication](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#webhook-token-authentication). When users call the Kubernetes API, a webhook passes an authentication token included in the request to IAM. The token, a base 64 signed URL, is generated by the AWS Command Line Interface ([AWS CLI](https://aws.amazon.com/cli/)).