In order to update a current Azure disk performance SKU, from Standard_LRS to Premium_LRS, for example, type:

az disk update --name yourdiskname --resource-group yourresourcegroup --sku Premium_LRS

After an initial deployment, you might find yourself in need to change the size of the Azure managed disk you’ve just deployed. For example, if you want to change the size of it to 64GB, type:

az disk update --resource-group yourresourcegroup --name yourdiskname --size-gb 64