Update install-blob-csi-driver.md

Author: andyzhangx

docs/install-blob-csi-driver.md

@@ -1,5 +1,8 @@
 ## Install Azure Blob Storage CSI driver on a Kubernetes cluster
-
+> Note: 
+>  - kubectl install method only works on AKS, capz, aks-engine clusters.
+>  - please use helm install method for more customization, e.g. Azure Stack, RedHat OpenShift support.
+> 
  - [install CSI driver master version](./install-csi-driver-master.md) (only for testing purpose)
  - [install v1.19.0 CSI driver](./install-csi-driver-v1.1999999999.0.md)
  - [install v1.18.0 CSI driver](./install-csi-driver-v1.18.0.md)