Update azure-disks-dynamic-pv.md

Added a note indicating that managed disks are billed by SKU and that the performance of Premium managed disks depends on the SKU.

Author: nmackenzie

articles/aks/azure-disks-dynamic-pv.md

@@ -34,6 +34,9 @@ default (default)   kubernetes.io/azure-disk   1h
 managed-premium     kubernetes.io/azure-disk   1h
 ```
 
+> [!NOTE]
+> Persistent volume claims are specified in GiB but Azure managed disks are billed by SKU of a specific size. These SKUs range from 32GiB for S4 or P4 disks to 4TiB for S50 or P50 disks. Furthermore, the throughput and IOPS performance of a Premium managed disk depends on the both the SKU and the instance size of the nodes in the AKS cluster. See [Pricing and Performance of Managed Disks][managed-disk-pricing-performance].
+
 ## Create persistent volume claim
 
 A persistent volume claim (PVC) is used to automatically provision storage based on a storage class. In this case, a PVC can use one of the pre-created storage classes to create a standard or premium Azure managed disk.
@@ -109,6 +112,7 @@ Learn more about Kubernetes persistent volumes using Azure disks.
 [kubernetes-disk]: https://kubernetes.io/docs/concepts/storage/storage-classes/#new-azure-disk-storage-class-starting-from-v172
 [kubernetes-storage-classes]: https://kubernetes.io/docs/concepts/storage/storage-classes/
 [kubernetes-volumes]: https://kubernetes.io/docs/concepts/storage/persistent-volumes/
+[managed-disk-pricing-performance]: https://azure.microsoft.com/en-us/pricing/details/managed-disks/
 
 <!-- LINKS - internal -->
 [azure-files-pvc]: azure-files-dynamic-pv.md