The hyper-converged Azure Stack HCI solution allows you to activate the Azure Kubernetes Service orchestrator in an on-premises environment (AKS) for running containerized applications at scale. This article explores how Azure Kubernetes in Azure Stack HCI environment offers the possibility of hosting Linux and Windows containers in your datacenter, going to explore the main benefits of this solution.
Before going into the specifics of AKS in the Azure Stack environment, a summary of the solutions involved is reported.
What is Kubernetes?
Kubernetes, also known as "k8s", provides automated orchestration of containers, improving its reliability and reducing the time and resources required in the DevOps field, through:
- Generally simpler deployments that allow automatic implementations and rollbacks.
- Better application management with the ability to monitor the status of services to avoid implementation errors. In fact,, the various features include service integrity checks, with the ability to restart containers that are not running or that are blocked, allowing to advertise to clients only the services that have started correctly.
- Ability to scale automatically based on usage and, exactly the same as for containers, manage the cluster environment in a declarative manner, allowing version-controlled and easily replicable configuration.
Figure 1 – Kubernetes cluster with related architecture components
What is Azure Kubernetes Service (AKS)?
Azure Kubernetes Service (AKS) is the fully managed Azure service that allows the activation of a Kubernetes cluster, ideal for simplifying the deployment and management of microservices-based architectures. Thanks to the features offered by AKS it is possible to scale automatically according to the use, use controls to ensure the integrity of the services, implement load balancing policies and manage secrets. The use of this managed service is integrated with the container development and deployment pipelines.
Figure 2 - Azure Kubernetes Service architecture example (AKS)
What is Azure Stack HCI?
Azure Stack HCI is the solution that allows you to create a hyper-converged infrastructure (HCI) for the execution of workloads in an on-premises environment and which provides for a strategic connection to Azure services. This is a hyper-converged infrastructure (HCI), where different hardware components are removed, substitutes from the software, able to combine the layer of compute, storage and network in one solution. In this way there is a transition from a traditional "three tier" infrastructure, composed of network switches, appliance, physical systems with onboard hypervisors, storage fabric and SAN, toward hyper-converged infrastructure (HCI).
Figure 3 – "Three Tier" Infrastructure vs Hyper-Converged Infrastructure (HCI)
What is AKS in Azure Stack HCI?
AKS in the Azure Stack HCI environment is a Microsoft implementation of AKS, which automates the deployment and management of containerized applications.
Microsoft, after introducing AKS as a service in Azure, has extended its availability also to on-premises environments. However, there are some important differences:
- In Azure, Microsoft manages the control plane of each AKS cluster. Furthermore, the cluster nodes (management node and worker node) run on Azure virtual machines or on Azure virtual machine scale sets.
- In an on-premises environment , the customer manages the entire environment, where the AKS cluster nodes are running on virtual machines hosted on the hyper-converged infrastructure.
AKS architecture on Azure Stack HCI
The implementation of AKS in Azure Stack HCI consists of two types of clusters:
- A management cluster of AKS. This cluster acts as a dedicated control plane for managing Kubernetes clusters running on the hyper-converged platform. This cluster consists of Linux virtual machines, that host Kubernetes system components such as API servers and load balancers.
- One or more Kubernetes clusters. These clusters consist of control nodes and worker nodes. Control nodes are implemented as Linux virtual machines, with API server and load balancers that satisfy the requests of Azure Stack HCI users. Workloads are distributed on Linux or Windows OS-based worker nodes.
Figure 4 - AKS architecture on Azure Stack HCI
Each Kubernetes cluster runs on its own dedicated set of virtual machines, protected by hypervisor-based isolation, allowing you to securely share the same physical infrastructure even in scenarios that require workload isolation.
AKS on Azure Stack HCI supports both Linux-based and Windows-based containers. When you create a Kubernetes cluster you simply need to specify the type of container you intend to run and on the hyper-converged platform the installation procedure of the required operating system is automatically started on the nodes of the Kubernetes cluster .
Benefits of AKS on Azure Stack HCI
AKS simplifies the deployment of Kubernetes clusters by providing a layer of abstraction that can mask some of the more challenging implementation details.
Among the main benefits of AKS in the Azure Stack HCI environment we find:
- Simplified deployments of containerized apps in a cluster environment. Using the Windows Admin Center you have a guided installation process of the AKS management cluster. Windows Admin Center also facilitates the installation of individual Kubernetes clusters that contain worker nodes, through an automatic installation process of all relevant software components, including management tools such as kubectl.
- Ability to scale horizontally to manage computational resources, adding or removing Kubernetes cluster nodes.
- Simplified management of cluster resource storage and network configurations.
- Automatic updates of cluster nodes to the latest version of Kubernetes available. Microsoft manages the Windows Server and Linux images for the cluster nodes and updates them monthly.
- Strategic connection, using Azure Arc, to Azure services such as: Microsoft Azure Monitor, Azure Policy, and Azure Role-Based Access Control (RBAC).
- Centralized management of Kubernetes clusters and related workloads through the Azure portal, thanks to the adoption of Azure Arc for Kubernetes. Azure portal-based management also integrates traditional Kubernetes administration tools and interfaces, like the command line utility kubectl and the Kubernetes dashboard.
- Managing the automatic failover of virtual machines acting as Kubernetes cluster nodes if there is a localized failure of the underlying physical components. This complements the high availability inherent in Kubernetes, able to automatically restart containers in failed state.
Conclusions
Thanks to Azure Stack HCI, the adoption of container-based application architectures can be hosted directly in your own datacenter, adopting the same Kubernetes management experience that you have with the managed service present in the Azure public cloud. The deployment process is also very simplified and intuitive. Furthermore, Azure Stack HCI allows you to further improve the agility and resilience of Kubernetes deployments in an on-premises environment.
