Merge pull request #205571 from dlepow/apimha

[APIM] High availability conceptual article

Author: tamarakhader

articles/api-management/TOC.yml

@@ -68,6 +68,9 @@
         href: api-management-gateways-overview.md
       - name: Self-hosted gateway
         href: self-hosted-gateway-overview.md
+      - name: High availability
+        href: high-availability.md
+        displayName: reliability, resilience, resiliency  
       - name: Networking
         href: virtual-network-concepts.md
       - name: Security
@@ -80,6 +83,7 @@
               href: authentication-authorization-overview.md
       - name: Observability
         href: observability.md
+        displayName: monitoring
       - name: DevOps and CI/CD
         href: devops-api-development-templates.md  
       - name: APIs

articles/api-management/high-availability.md

@@ -0,0 +1,76 @@
+---
+title: Ensure reliability of your Azure API Management instance
+titleSuffix: Azure API Management
+description: Learn how to use Azure reliability features including availability zones and multiregion deployments to make your Azure API Management service instance resilient to cloud failures.
+author: dlepow
+ms.service: api-management
+ms.topic: conceptual
+ms.date: 09/27/2022
+ms.author: danlep
+---
+
+# Ensure API Management availability and reliability
+
+
+This article introduces service capabilities and considerations to ensure that your API Management instance continues to serve API requests if Azure outages occur. 
+
+API Management supports the following key service capabilities that are recommended for [reliable and resilient](../availability-zones/overview.md) Azure solutions. Use them individually, or together, to improve the availability of your API Management solution:
+
+* **Availability zones**, to provide resilience to datacenter-level outages
+
+* **Multi-region deployment**, to provide resilience to regional outages
+
+> [!NOTE]
+> API Management supports availability zones and multi-region deployment in the **Premium** service tier.  
+
+## Availability zones
+
+Azure [availability zones](../availability-zones/az-overview.md) are physically separate locations within an Azure region that are tolerant to datacenter-level failures. Each zone is composed of one or more datacenters equipped with independent power, cooling, and networking infrastructure. To ensure resiliency, a minimum of three separate availability zones are present in all availability zone-enabled regions.  
+
+
+Enabling [zone redundancy](../availability-zones/migrate-api-mgt.md) for an API Management instance in a supported region provides redundancy for all [service components](api-management-key-concepts.md#api-management-components): gateway, management plane, and developer portal. Azure automatically replicates all service components across the zones that you select. 
+
+When you enable zone redundancy in a region, consider the number of API Management scale [units](upgrade-and-scale.md) that need to be distributed. Minimally, configure the same number of units as the number of availability zones, or a multiple so that the units are distributed evenly across the zones. For example, if you select 3 availability zones in a region, you could have 3 units so that each zone hosts one unit.
+
+> [!NOTE]
+> Use the [capacity](api-management-capacity.md) metric and your own testing to decide on the number of scale units that will provide the gateway performance for your needs. Learn more about [scaling and upgrading](upgrade-and-scale.md) your service instance.
+
+## Multi-region deployment
+
+[!INCLUDE [api-management-multi-region-concepts](../../includes/api-management-multi-region-concepts.md)]
+
+## Combine availability zones and multi-region deployment
+
+The combination of availability zones for redundancy within a region, and multi-region deployments to improve the gateway availability if there is a regional outage, helps enhance both the reliability and performance of your API Management instance.
+
+Examples:
+
+* Use availability zones to improve the resilience of the primary region in a multi-region deployment
+
+* Distribute scale units across availability zones and regions to enhance regional gateway performance
+
+
+## SLA considerations
+
+API Management provides an SLA of 99.99% when you deploy at least one unit in two or more availability zones or regions. For more information, see [Pricing](https://azure.microsoft.com/pricing/details/api-management/).
+
+> [!NOTE]
+> While Azure continually strives for highest possible resiliency in SLA for the cloud platform, you must define your own target SLAs for other components of your solution.
+
+## Backend availability
+
+Depending on where and how your backend services are hosted, you may need to set up redundant backends in different regions to meet your requirements for service availability. You can manage regional backends and handle failover through API Management to maintain availability. For example:  
+
+* In multi-region deployments, use [policies to route requests](api-management-howto-deploy-multi-region.md#-route-api-calls-to-regional-backend-services) through regional gateways to regional backends. 
+
+* Configure policies to route requests conditionally to different backends if there is backend failure in a particular region.
+
+* Use caching to reduce failing calls.
+
+For details, see the blog post [Back-end API redundancy with Azure API Manager](https://devblogs.microsoft.com/premier-developer/back-end-api-redundancy-with-azure-api-manager/).
+
+## Next steps
+
+* Learn more about [resiliency in Azure](../availability-zones/overview.md)
+* Learn more about [designing reliable Azure applications](/azure/architecture/framework/resiliency/app-design)
+* Read [API Management and reliability](/azure/architecture/framework/services/networking/api-management/reliability) in the Azure Well-Architected Framework