docs: Add a note about zonal balancing (#5531)

website/content/en/docs/concepts/scheduling.md

@@ -352,6 +352,10 @@ The three supported `topologyKey` values that Karpenter supports are:
 
 See [Pod Topology Spread Constraints](https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/) for details.
 
+{{% alert title="Note" color="primary" %}}
+NodePools do not attempt to balance or rebalance the availability zones for their nodes. Availability zone balancing may be achieved by defining zonal Topology Spread Constraints for Pods that require multi-zone durability, and NodePools will respect these constraints while optimizing for compute costs.
+{{% /alert %}}
+
 ## Pod affinity/anti-affinity
 
 By using the `podAffinity` and `podAntiAffinity` configuration on a pod spec, you can inform the Karpenter scheduler of your desire for pods to schedule together or apart with respect to different topology domains. For example:

website/content/en/preview/concepts/scheduling.md

@@ -349,9 +349,12 @@ The three supported `topologyKey` values that Karpenter supports are:
 - `kubernetes.io/hostname`
 - `karpenter.sh/capacity-type`
 
-
 See [Pod Topology Spread Constraints](https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/) for details.
 
+{{% alert title="Note" color="primary" %}}
+NodePools do not attempt to balance or rebalance the availability zones for their nodes. Availability zone balancing may be achieved by defining zonal Topology Spread Constraints for Pods that require multi-zone durability, and NodePools will respect these constraints while optimizing for compute costs.
+{{% /alert %}}
+
 ## Pod affinity/anti-affinity
 
 By using the `podAffinity` and `podAntiAffinity` configuration on a pod spec, you can inform the Karpenter scheduler of your desire for pods to schedule together or apart with respect to different topology domains. For example:

website/content/en/v0.30/concepts/scheduling.md

@@ -354,6 +354,10 @@ The three supported `topologyKey` values that Karpenter supports are:
 
 See [Pod Topology Spread Constraints](https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/) for details.
 
+{{% alert title="Note" color="primary" %}}
+NodePools do not attempt to balance or rebalance the availability zones for their nodes. Availability zone balancing may be achieved by defining zonal Topology Spread Constraints for Pods that require multi-zone durability, and NodePools will respect these constraints while optimizing for compute costs.
+{{% /alert %}}
+
 ## Pod affinity/anti-affinity
 
 By using the `podAffinity` and `podAntiAffinity` configuration on a pod spec, you can inform the provisioner of your desire for pods to schedule together or apart with respect to different topology domains. For example:

website/content/en/v0.31/concepts/scheduling.md

@@ -354,6 +354,10 @@ The three supported `topologyKey` values that Karpenter supports are:
 
 See [Pod Topology Spread Constraints](https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/) for details.
 
+{{% alert title="Note" color="primary" %}}
+NodePools do not attempt to balance or rebalance the availability zones for their nodes. Availability zone balancing may be achieved by defining zonal Topology Spread Constraints for Pods that require multi-zone durability, and NodePools will respect these constraints while optimizing for compute costs.
+{{% /alert %}}
+
 ## Pod affinity/anti-affinity
 
 By using the `podAffinity` and `podAntiAffinity` configuration on a pod spec, you can inform the provisioner of your desire for pods to schedule together or apart with respect to different topology domains. For example:

website/content/en/v0.32/concepts/scheduling.md

@@ -351,6 +351,10 @@ The three supported `topologyKey` values that Karpenter supports are:
 
 See [Pod Topology Spread Constraints](https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/) for details.
 
+{{% alert title="Note" color="primary" %}}
+NodePools do not attempt to balance or rebalance the availability zones for their nodes. Availability zone balancing may be achieved by defining zonal Topology Spread Constraints for Pods that require multi-zone durability, and NodePools will respect these constraints while optimizing for compute costs.
+{{% /alert %}}
+
 ## Pod affinity/anti-affinity
 
 By using the `podAffinity` and `podAntiAffinity` configuration on a pod spec, you can inform the Karpenter scheduler of your desire for pods to schedule together or apart with respect to different topology domains. For example:

website/content/en/v0.33/concepts/scheduling.md

@@ -352,6 +352,10 @@ The three supported `topologyKey` values that Karpenter supports are:
 
 See [Pod Topology Spread Constraints](https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/) for details.
 
+{{% alert title="Note" color="primary" %}}
+NodePools do not attempt to balance or rebalance the availability zones for their nodes. Availability zone balancing may be achieved by defining zonal Topology Spread Constraints for Pods that require multi-zone durability, and NodePools will respect these constraints while optimizing for compute costs.
+{{% /alert %}}
+
 ## Pod affinity/anti-affinity
 
 By using the `podAffinity` and `podAntiAffinity` configuration on a pod spec, you can inform the Karpenter scheduler of your desire for pods to schedule together or apart with respect to different topology domains. For example: