[
    {
    "lun": 0,
    "name": "[concat(parameters('virtualMachineName'), '-datadisk1')]",
    "createOption": "attach",
    "managedDisk": {
        "id": "[resourceId('Microsoft.Compute/disks/', concat(parameters('virtualdisk1name')]"
    }
},
{
    "lun": 1,
    "name": "[concat(parameters('virtualMachineName'), '-datadisk2')]",
    "createOption": "attach",
    "managedDisk": {
        "id": "[resourceId('Microsoft.Compute/disks/', '-datadisk2'))]"
    }
},
{
    "lun": 2,
    "name": "[concat(parameters('virtualMachineName'), '-datadisk3')]",
    "createOption": "attach",
    "managedDisk": {
        "id": "[resourceId('Microsoft.Compute/disks/' ,'-datadisk3'))]"
    }
}