Broker cannot be upgraded if there is a single backend replica

Author: jlian

articles/iot-operations/deploy-iot-ops/howto-manage-update-uninstall.md

@@ -193,6 +193,9 @@ Azure IoT Operations supports upgrading instances to new versions as they're rel
 
 You can't upgrade from a preview installation to a GA version.
 
+> [!NOTE]
+> There's a known issue with upgrading Azure IoT Operations if the MQTT broker only has one backend replica. Only upgrade Azure IoT Operations if the Broker has more than one backend replica.
+
 ### [Azure portal](#tab/portal)
 
 1. In the [Azure portal](https://portal.azure.com), go to the resource group that contains your Azure IoT Operations instance, or search for and select **Azure IoT Operations**.

articles/iot-operations/troubleshoot/known-issues.md

@@ -29,6 +29,8 @@ This article lists the known issues for Azure IoT Operations.
 
   As a workaround, when deploying Azure IoT Operations with the [az iot ops init](/cli/azure/iot/ops#az-iot-ops-init) command, you can include the `--broker-config-file` parameter with a JSON configuration file for the MQTT broker. For more information, see [Advanced MQTT broker config](https://github.com/Azure/azure-iot-ops-cli-extension/wiki/Advanced-Mqtt-Broker-Config) and [Configure core MQTT broker settings](../manage-mqtt-broker/howto-configure-availability-scale.md).
 
+- If a Broker only has one backend replica, upgrading Azure IoT Operations might fail. Only upgrade Azure IoT Operations if the Broker has more than one backend replica.
+
 - Even though the MQTT broker's [diagnostics](../manage-mqtt-broker/howto-broker-diagnostics.md) produces telemetry on its own topic, you might still get messages from the self-test when you subscribe to `#` topic.
 
 - Deployment might fail if the **cardinality** and **memory profile** values are set to be too large for the cluster. To resolve this issue, set the replicas count to `1` and use a smaller memory profile, like `low`.