Merge pull request #176513 from anastasia-ms/overflow2

Overflow scenario for device registration

Author: v-andreaco

articles/iot-dps/tutorial-provision-multiple-hubs.md

@@ -1,9 +1,9 @@
 ---
 title: Tutorial - Provision devices across load balanced hubs using Azure IoT Hub Device Provisioning Service
-description: This tutorial demonstrates how Device Provisioning Service (DPS) enables automatic device provisioning across load balanced IoT hubs in Azure Portal
-author: wesmc7777
-ms.author: wesmc
-ms.date: 11/12/2019
+description: This tutorial demonstrates how Device Provisioning Service (DPS) enables automatic device provisioning across load balanced IoT hubs in the Azure portal.
+author: anastasia-ms
+ms.author: v-stharr
+ms.date: 10/18/2021
 ms.topic: tutorial
 ms.service: iot-dps
 services: iot-dps
@@ -32,20 +32,25 @@ Follow the steps in the [Provision device to a hub](tutorial-provision-device-to
 
 ## Add an enrollment list entry to the second device
 
-The enrollment list tells the Device Provisioning Service which method of attestation (the method for confirming a device identity) it is using with the device. The next step is to add an enrollment list entry for the second device. 
+The enrollment list tells the Device Provisioning Service which method of attestation (the method for confirming a device identity) it is using with the device. The next step is to add an enrollment list entry for the second device.
 
-1. In the page for your Device Provisioning Service, click **Manage enrollments**. The **Add enrollment list entry** page appears. 
+1. In the page for your Device Provisioning Service, click **Manage enrollments**. The **Add enrollment list entry** page appears.
 2. At the top of the page, click **Add**.
-2. Complete the fields and then click **Save**.
+3. Complete the fields and then click **Save**.
 
 ## Set the Device Provisioning Service allocation policy
 
 The allocation policy is a Device Provisioning Service setting that determines how devices are assigned to an IoT hub. There are three supported allocation policies: 
 
 1. **Lowest latency**: Devices are provisioned to an IoT hub based on the hub with the lowest latency to the device.
-2. **Evenly weighted distribution** (default): Linked IoT hubs are equally likely to have devices provisioned to them. This is the default setting. If you are provisioning devices to only one IoT hub, you can keep this setting. 
+2. **Evenly weighted distribution** (default): Linked IoT hubs are equally likely to have devices provisioned to them. This is the default setting. If you are provisioning devices to only one IoT hub, you can keep this setting. If you plan to use on IoT hub, but expect to increase the number of hubs as the number of devices increases, it's important to note that,  when assigning to an IoT Hub, the policy doesn't take into account previously registered devices. All linked hubs hold an equal chance of getting a device registration based on the weight of the linked IoT Hub. However, if an IoT hub has reached its device capacity limit, it will no longer receive device registrations. You can, however, adjust the weight of allocation for each linked IoT Hub.
+
 3. **Static configuration via the enrollment list**: Specification of the desired IoT hub in the enrollment list takes priority over the Device Provisioning Service-level allocation policy.
 
+### How the allocation policy assigns devices to IoT Hubs
+
+It may be desirable to use only one IoT Hub, until a specific number of devices is reached. In that scenario, it's important to note that, once a new IoT Hub is added, a new device has the potential to be provisioned to any one of the IoT Hubs. If you wish to balance all devices, registered and unregistered, then you'll need to re-provision all devices.
+
 Follow these steps to set the allocation policy:
 
 1. To set the allocation policy, in the Device Provisioning Service page click **Manage allocation policy**.