Concepts of Azure high availability

Go back to AZ-304 Tutorials

In this tutorial we will learn about Azure high availability with defining availability requirements and planning high availability architecture.

Azure High Availability

Azure high availability refers to the ability of a system or application to remain operational and accessible even in the face of disruptions or failures. This is achieved through a combination of redundancy, failover mechanisms, and automatic recovery processes. Here are some key concepts related to Azure high availability:

Availability Sets: Azure Availability Sets ensure that resources are distributed across multiple fault domains and update domains, which helps to prevent single points of failure. Fault domains are sets of hardware that share a common power source and network switch, while update domains represent groups of virtual machines that can be updated in stages.
Load Balancing: Azure Load Balancer distributes incoming traffic across multiple virtual machines, which helps to improve performance and availability. It can be configured to use either TCP or HTTP traffic, and supports various load balancing algorithms, including round-robin, least connections, and source IP affinity.
Azure Traffic Manager: Azure Traffic Manager is a DNS-based traffic load balancer that routes traffic to the most appropriate endpoint based on a set of rules. It supports multiple traffic-routing methods, including performance-based, geographic, and weighted round-robin.
Virtual Machine Scale Sets: Azure Virtual Machine Scale Sets allow you to automatically scale out or in virtual machines based on demand. This helps to ensure that applications remain available during periods of high traffic or usage.
Azure Site Recovery: Azure Site Recovery is a disaster recovery solution that replicates virtual machines and physical servers to a secondary site. In the event of a disaster, applications can be quickly failed over to the secondary site, minimizing downtime.
Backup and Restore: Azure provides a range of backup and restore options for virtual machines, databases, and other resources. This helps to ensure that data is protected against data loss or corruption, and can be quickly restored in the event of a failure.

Technical components enabling high availability

There are several technical components in Azure that enable high availability:

Azure Availability Zones: Availability Zones are physically separate datacenters within an Azure region, each with independent power, cooling, and networking. Deploying resources across multiple Availability Zones can provide additional fault tolerance, ensuring that your application remains available even in the event of a datacenter-level failure.
Azure Virtual Machine Scale Sets: Virtual Machine Scale Sets allow you to easily deploy and manage a group of identical VMs, automatically scaling the number of VMs up or down based on demand. This helps to ensure that your application can handle spikes in traffic while remaining highly available.
Azure Load Balancer: Azure Load Balancer distributes incoming traffic across multiple VMs or instances to prevent any one instance from becoming overloaded or overwhelmed. This can be done using a variety of load balancing algorithms such as round-robin, source IP affinity, or session affinity.
Azure Traffic Manager: Azure Traffic Manager allows you to distribute traffic across multiple endpoints, such as Azure VMs or cloud services, based on a variety of routing methods, including geographic location, performance, or round-robin.
Azure Application Gateway: Azure Application Gateway provides advanced load balancing capabilities for web applications, including SSL offloading, cookie-based session affinity, and URL-based routing. It also includes features such as WAF (Web Application Firewall) and SSL termination.
Azure Site Recovery: Azure Site Recovery provides disaster recovery capabilities for applications and services running on Azure. It allows you to replicate your workloads to a secondary Azure region, providing near-zero RPO (Recovery Point Objective) and RTO (Recovery Time Objective) in the event of a disaster.
Azure Backup: Azure Backup provides backup and recovery capabilities for your Azure VMs, Azure file shares, and SQL Server running on Azure VMs, helping to protect your data against accidental deletion, corruption, or ransomware attacks.

Azure High Availability Checklist

Here is a checklist for achieving high availability in Azure:

Identify critical components: Identify the components of your application or service that are critical to its operation and availability.
Use Azure Availability Zones: Deploy resources across multiple Azure Availability Zones to provide additional fault tolerance and ensure your application remains available even in the event of a datacenter-level failure.
Use Azure Load Balancer: Use Azure Load Balancer to distribute incoming traffic across multiple VMs or instances to prevent any one instance from becoming overloaded or overwhelmed.
Use Azure Traffic Manager: Use Azure Traffic Manager to distribute traffic across multiple endpoints, such as Azure VMs or cloud services, based on a variety of routing methods.
Use Azure Virtual Machine Scale Sets: Use Azure Virtual Machine Scale Sets to automatically scale the number of VMs up or down based on demand, ensuring that your application can handle spikes in traffic while remaining highly available.
Use Azure Application Gateway: Use Azure Application Gateway to provide advanced load balancing capabilities for web applications, including SSL offloading, cookie-based session affinity, and URL-based routing.
Use Azure Site Recovery: Use Azure Site Recovery to replicate your workloads to a secondary Azure region, providing near-zero RPO and RTO in the event of a disaster.
Use Azure Backup: Use Azure Backup to protect your data against accidental deletion, corruption, or ransomware attacks.
Use Azure Monitor: Use Azure Monitor to monitor the health and performance of your Azure resources, including VMs, storage accounts, and application insights.
Test your high availability configuration: Regularly test your high availability configuration to ensure that it is working as expected and can handle failures without impacting the availability of your application or service.

Azure availability zones

Azure Availability Zones are unique physical locations within an Azure region that are designed to provide high availability and resiliency to applications and services. An Azure region typically consists of multiple datacenters that are connected by a high-speed network, but Availability Zones are separate datacenters with independent power, cooling, and networking infrastructure.

By deploying resources across multiple Availability Zones within a region, you can protect your applications and services from datacenter-level failures, such as power outages, network failures, or natural disasters. Azure guarantees that at least 99.99% of virtual machines running in an Availability Zone will be available, and each zone is isolated from the others to minimize the risk of a regional outage.

When you deploy a virtual machine, storage account, or any other Azure resource to an Availability Zone, Azure automatically replicates your data to other zones within the same region, ensuring that your data remains available and accessible in the event of a zone-level failure.

Azure Availability Zones are currently available in select regions, and not all Azure services support deployment to Availability Zones. However, Azure provides a Service Level Agreement (SLA) of 99.99% for virtual machines running in an Availability Zone, making it an ideal choice for mission-critical applications that require high availability and resiliency.

Azure high availability concept in Az-304 online course

AZ-304 Exam Practice Questions

Question: You have deployed a virtual machine in an Azure region that supports Availability Zones. Which of the following actions can you take to ensure high availability for your VM?

A. Deploy the VM to a single Availability Zone

B. Deploy the VM to multiple Availability Zones

C. Deploy the VM to multiple regions

D. Deploy the VM to a single datacenter

Answer: B. Deploy the VM to multiple Availability Zones.

Explanation: By deploying the VM to multiple Availability Zones within the same region, you can protect it from zone-level failures and ensure high availability.

Question: You have deployed an Azure Storage account in an Azure region that supports Availability Zones. Which of the following options will provide the highest level of availability for your data?

A. Store your data in a single storage account

B. Store your data in multiple storage accounts within the same region

C. Store your data in multiple Availability Zones within the same region

D. Store your data in multiple regions

Answer: C. Store your data in multiple Availability Zones within the same region.

Explanation: By storing your data in multiple Availability Zones within the same region, you can ensure that your data remains available in the event of a zone-level failure.

Question: You have deployed an Azure App Service to an Azure region that supports Availability Zones. Which of the following options can you use to ensure high availability for your application?

A. Deploy the App Service to a single Availability Zone

B. Deploy the App Service to multiple Availability Zones

C. Deploy the App Service to multiple regions

D. Deploy the App Service to a single datacenter

Answer: B. Deploy the App Service to multiple Availability Zones.

Explanation: By deploying the App Service to multiple Availability Zones within the same region, you can ensure high availability for your application.

Question: You are deploying a new application to Azure that requires high availability. Which of the following Azure services supports deployment to Availability Zones?

A. Azure Cosmos DB

B. Azure SQL Database

C. Azure Virtual Machines

D. Azure Kubernetes Service

Answer: C. Azure Virtual Machines.

Explanation: While Azure Cosmos DB, Azure SQL Database, and Azure Kubernetes Service do not currently support deployment to Availability Zones, Azure Virtual Machines can be deployed to multiple Availability Zones within the same region to ensure high availability.

Question: You are designing an Azure solution that requires high availability and disaster recovery. Which of the following options can you use to replicate data between two regions?

A. Azure Virtual Network Peering

B. Azure Site Recovery

C. Azure Load Balancer

D. Azure ExpressRoute

Answer: B. Azure Site Recovery.

Explanation: Azure Site Recovery provides a disaster recovery solution that replicates virtual machines and physical servers between regions, ensuring high availability and business continuity in the event of a regional outage. Azure Virtual Network Peering, Azure Load Balancer, and Azure ExpressRoute do not provide replication capabilities for disaster recovery.