Add warning about multi-DC scenario being unsupported

Author: sasank-chaganty

articles/azure-arc/data/plan-azure-arc-data-services.md

@@ -92,6 +92,7 @@ You can deploy Azure Arc-enabled data services on various types of Kubernetes cl
 - Additional [partner-validated Kubernetes distributions](./validation-program.md)
 
 > [!IMPORTANT]
+> * Currently, only one Azure Arc data controller per Kubernetes cluster is supported.
 > * The minimum supported version of Kubernetes is v1.21. For more information, see the "Known issues" section of [Release notes - Azure Arc-enabled data services](./release-notes.md#known-issues).
 > * The minimum supported version of OCP is 4.8.
 > * If you're using Azure Kubernetes Service, your cluster's worker node virtual machine (VM) size should be at least Standard_D8s_v3 and use Premium Disks.