Azure Availability Zones: Achieve High Availability

One of the main reasons why organizations decide to move their resources to a cloud provider is to guarantee as much reliability and availability for their services as possible. The distribution of workloads and resources among physically separated datacenters guarantees business continuity even if the primary data center becomes temporarily unavailable. Azure Availability Zones can be employed when physical isolation is required to provide high availability to different resources over Microsoft Azure.

Azure Availability Zone Definition

Organizations deploying their resources over the Azure cloud should choose the region that best fits their needs based on different considerations such as service features and requisites, data location, compliance requirements, product pricing and network latency.

An Azure region is a set of data centers deployed within a latency-defined perimeter and connected through a dedicated, regional low-latency network. Within each Azure region are unique physical locations called Availability Zones. Each Availability Zone is comprised of one or more data centers equipped with independent power, cooling and networking resources.

Azure services that support Availability Zones are divided into zonal services, where a resource is pinned to a specific zone and zone-redundant services, where Azure replicates automatically across zones. Regions and services that support Availability Zones using Azure are detailed in the following link.

Availability zones protect data and applications from datacenter failures as there are minimum three separate zones in all enabled regions to achieve failover. Each separate zone has one or more datacenter, independent networking, cooling and power hence zone-redundant services replicate data and applications to protect from single-points-of-failure and achieve 99.99% uptime.

Datacenter failures are handled properly because the Availability Zone in Azure is a combination of a fault domain and an update domain. When three or more VMs are created in an Azure region for example, they are distributed across three fault domains and three update domains. Azure platform thus ensures that VMs in different zones are not updated at the same time. You can achieve business continuity and high availability by building your application architecture with the combination of Availability Zones with Azure region pairs.

Availability Zones Vs. Availability Sets

In addition to Availability Zones, Azure offers other high-availability options such as Availability Sets. The main difference between Availability Zones and Availability Sets is that, in terms of service continuity, Availability Zones guarantee protection against a complete data center failure, whereas Availability Sets cover only potential failures within the same data center. This means that Availability Zones encompass 99.99% of the Service Level Agreement (SLA) versus the 99.95% coverage offered by Availability Sets.

Additionally, Availability Zones support different Azure services such as virtual machines (VMs), ExpressRoutes, SQL databases and virtual private network (VPN) gateways, while Availability Sets are designed to work only with VMs.

Availability Zone Set Up in Azure

To configure an Availability Zone for a VM from the Azure portal, complete the following steps:

  1. Log on to your Azure account.
  1. Add a new virtual machine through the Create a virtual machine wizard.
  1. Under the Basics tab, locate the Availability options field. Select Availability zone from the drop-down list. Note that not all regions support Availability Zones. If the selected Region does not support Availability Zones, the following message will be displayed: “No availability zones are available for the location you have selected”.
  1. Expand the Availability zone drop-down list, and select one of the numbered zones. In this example, a new virtual machine will be deployed in the East US region which offers three Availability Zones. Zone number 1 is the zone that will be configured.

Figure 1 - Azure Availability Zones

  1. Complete the rest of the configuration fields according to your requirements, and click on the Review + create button. Once the validation process is complete, click the Create button.
  1. Once the deployment has been carried out, click the Go to resource button. The summary view includes information about the location and the Availability Zone of the VM.

Figure 2 - Azure Availability Zones

Availability Zones can also be configured using Azure PowerShell .

High Availability and Parallels RAS

Parallels® Remote Application Server (RAS) can be deployed easily over Azure due to its prebuilt Azure virtual machine templates, simple configuration wizards and built-in automation capabilities. Components such as HALBs (High Availability Load Balancers), Secure Client Gateways and Publishing Agents should be duplicated to prevent any infrastructure server from becoming a single point of failure. Organizations may opt to configure Availability Zones for these components depending on the required SLA, thus increasing the reliability and availability of their Parallels RAS deployment.

Parallels RAS also provides multi-tenancy support which allows administrators to manage multiple Parallels RAS environments centrally. Additionally, Parallels RAS streamlines the onboarding processes of new customers since certain infrastructure components such as HALBs and Secure Client Gateways can be shared among different tenants. Administrators may decide to configure these shared resources within different Availability Zones to increase the responsiveness of their Parallels RAS environment.

Like VMs, certain networking services such as Azure Firewall, Standard Load Balancer, VPN Gateway and ExpressRoute Gateways can be configured using Availability Zones. When working with hybrid or cloud Parallels RAS deployments, administrators can guarantee a high-availability configuration not only for infrastructure servers but also for those networking resources involved.

References

Microsoft – Manage Availability 

Microsoft – Availability Zones Overview

Microsoft – Availability Zones

Experience Parallels RAS with a 30-day trial.