Azure Disaster Recovery Architecture Simplified with Azure Site Recovery

Azure Site Recovery is a key component of Azure Disaster Recovery Architecture, allowing you to replicate and failover workloads between Azure regions.

It supports replication of on-premises VMs to Azure, as well as replication of Azure VMs between regions.

This simplifies disaster recovery planning and execution, enabling you to focus on business continuity rather than complex infrastructure management.

With Azure Site Recovery, you can replicate entire VMs, including their operating systems, applications, and data, to a secondary region.

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To set up disaster recovery for Azure VMs, you'll need one or more Azure VMs in a supported source region, running any supported operating system. These VMs can be managed or have non-managed disks spread across storage accounts.

The components involved in disaster recovery for Azure VMs include VMs in the source region, source VM storage, source VM networks, cache storage account, and target resources. Each component has specific requirements, such as VMs being located in one or more subnets in a virtual network (VNet) in the source region.

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Here's a breakdown of the components involved in disaster recovery for Azure VMs:

Azure VMs in a supported source region are required for disaster recovery, and they can be running any supported operating system.

A cache storage account is necessary in the source network to store VM changes before being sent to target storage, ensuring minimal impact on production applications.

You need to have one or more Azure VMs in a supported source region, with managed or non-managed disks spread across storage accounts.

VMs can be located in one or more subnets in a virtual network (VNet) in the source region.

During replication, target resources are used, and when a failover occurs, they are used again.

To set up target resources, Site Recovery can do it by default, or you can create and customize them.

In the target region, you need to check if you can create VMs and if your subscription has enough resources to support VM sizes.

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Azure Site Recovery replication appliance is the basic building block of the entire on-premises infrastructure.

It oversees all end-to-end Site Recovery activities, including monitoring the health of protected machines, data replication, and automatic updates.

The replication appliance hosts various crucial components, such as a proxy server, discovered items, re-protection server, process server, Recovery Service agent, Site Recovery provider, and replication service.

Mobility Service is installed on each physical server that you replicate, and we recommend allowing automatic installation of the service.

The following components are required for physical machine disaster recovery to Azure:

Replicated data from on-premises machines is stored in Azure storage, and Azure VMs are created with the replicated data when you run a failover from on-premises to Azure.

The Azure VMs connect to the Azure virtual network when they're created.

Here is a summary of the components involved in disaster recovery for Azure VMs:

Target Resources play a crucial role in Azure Disaster Recovery Architecture. You can create target resources automatically when you enable replication for a VM, which is a convenient feature of Site Recovery.

Site Recovery creates a new resource group in the target region, with an "asr" suffix, by default. This resource group will hold the VMs after a failover occurs. You can also create a custom resource group if needed.

A network mapping is created between the source and target virtual networks, and vice versa. Site Recovery creates a new VNet and subnet in the target region, with the "asr" suffix. This ensures that the replicated VMs are located in the correct network after a failover.

You can modify target settings as you enable replication, including the target subscription, resource group, VNet, and storage account. The default SKU for the target region VM is the same as the SKU of the source VM, or the next best available SKU.

Here is a summary of the default target resource settings:

You can also modify target settings after replication is already working, but some settings, such as the availability type, cannot be updated once replication is in progress.

Azure Disaster Recovery Architecture is a crucial aspect of ensuring business continuity and minimizing downtime in the event of a disaster.

Hyper-V Replica is a replication option that creates and maintains copies of important VMs in a secondary site, but it's far from perfect. This is because not all enterprises can afford a secondary data center.

Azure Site Recovery (ASR) is a service that allows your VMs to failover into the Azure public cloud, making it a more feasible option for disaster recovery. This service was initially intended to be a tool for orchestrating and automating replication and maintenance in case of both planned and unplanned on-premises and secondary data centers outages.

To ensure Azure connection with primary and secondary sites, you need to establish connections that will serve as the means to monitor the state of secured areas.

You can select the VMs you need to have protected with replication and define replication parameters. This includes developing a coherent recovery plan that includes all stages necessary for switching to a secondary site, VMs boot sequence in a secondary data center, various possible scripts, and their start sequence.

Azure Site Recovery replicates workloads running on both physical and virtual machines, safely and smoothly moving them from a primary site to a secondary destination.

Here are the key components of Azure Site Recovery:

Data protection and backup are crucial components of a robust disaster recovery architecture. Microsoft Azure combines the best of IaaS and PaaS to unlock various use cases, including data protection and disaster recovery.

Using Zerto with a public cloud like Azure simplifies data protection and disaster recovery. This combination helps businesses achieve IT resilience by minimizing risks and ensuring data recovery.

To ensure consistency and minimize data loss, Site Recovery takes crash-consistent snapshots of data by default. App-consistent snapshots can be specified for a frequency, and recovery points are created from the snapshots and stored in accordance with retention settings in the replication policy.

Recovery points are created from snapshots of VM disks taken at a specific point in time. This allows for the restoration of a VM in the target location with no corruption or data loss, ensuring consistency for the operating system and apps that run on the VM.

Here are the types of snapshots taken by Site Recovery:

Policy plays a crucial role in data protection and backup. You can manage and modify the settings of default replication policies as you enable replication.

The default settings for a replication policy include a recovery point retention period of one day, which means Site Recovery keeps recovery points for that duration.

High recovery point retention periods can have implications on storage costs, as more recovery points may need to be saved.

You can modify the settings as you enable replication, or create a replication policy at any time and then apply it when you enable replication.

Here's a summary of the default replication policy settings:

Microsoft Azure combines the best of IaaS and PaaS, making it a great choice for businesses looking to simplify their data protection and disaster recovery.

By using Zerto with a public cloud like Azure, businesses can unlock a wide range of use cases, from data protection and DR to workload migration, for their infrastructure and/or application development.

With Azure, you can create recovery points from snapshots of VM disks taken at a specific point in time. This ensures that your VM starts with no corruption or data loss, and that the VM data is consistent for the operating system, and for apps that run on the VM.

Recovery points are created from snapshots of VM disks taken at a specific point in time. Site Recovery takes crash-consistent snapshots of data by default, and app-consistent snapshots if you specify a frequency for them.

Here's a summary of the replication policy settings in Azure:

App-consistent snapshots are more complex and take longer to complete than crash-consistent snapshots, but they're essential for ensuring that your data is consistent and up-to-date.

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A backup plan is essential for minimizing risks and ensuring data recovery in case of an emergency.

Databases often store vital information, so having a backup plan in place is crucial for maintaining business continuity.

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Full backups are a common type of backup, where a complete copy of the database is created.

They can be time-consuming and require a significant amount of storage space.

Incremental backups, on the other hand, only capture changes made since the last backup.

This method is faster and more efficient than full backups, but may not be suitable for all databases.

Database administrators can also use differential backups, which capture all changes made since the last full backup.

This method balances the speed of incremental backups with the comprehensiveness of full backups.

In common DB systems, backups can be performed using various methods, including physical and logical backups.

Physical backups involve copying the database files, while logical backups involve copying the database schema and data.

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To ensure a successful Azure disaster recovery architecture, you need to focus on connectivity and security. Site Recovery requires outbound connectivity to replicate VMs, and it never needs inbound connectivity.

For outbound connectivity, you need to allow specific URLs, which include storage, Microsoft Entra ID, replication, Service Bus, Key Vault, and Azure Automation URLs. Here are the specific URLs you need to allow:

You can also control access with Network Security Group rules, which should allow outbound access for replication traffic and use service tags instead of individual IP addresses.

Managing target resources is a crucial aspect of ensuring a seamless failover experience. You can modify target settings as you enable replication, but note that the default SKU for the target region VM is the same as the SKU of the source VM.

The dropdown list only shows relevant SKUs of the same family as the source VM (Gen 1 or Gen 2). This ensures that you can easily find a compatible option for your target VM.

You can also modify target settings after replication is already working. However, there are some limitations to be aware of. The availability type (single instance, set, or zone) cannot be updated once replication is in progress.

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To change this setting, you need to disable replication, modify the setting, and then reenable. This will allow you to ensure that your target resources are configured correctly for your specific needs.

Here's a quick summary of the target resource settings that can be modified:

A crash consistent snapshot captures data that was on the disk when the snapshot was taken, but it doesn't include anything in memory. This means it's like taking a picture of the data on your hard drive at a specific moment, without showing what's currently being worked on in your computer's RAM.

Site Recovery creates crash-consistent recovery points every five minutes by default, and this setting can't be modified. This is a built-in feature that helps ensure you have a recent backup in case something goes wrong.

Crash-consistent recovery points are usually sufficient for the replication of operating systems, and apps such as DHCP servers and print servers. Most apps can recover well from crash-consistent points, making them a reliable option for backup and recovery.

A crash-consistent snapshot contains the equivalent of the on-disk data that would be present if the system crashed or the power cord was pulled from the server at the instant that the snapshot was taken. This is a snapshot of your data in a frozen state, at a specific moment in time.

Outbound Connectivity (URLs) is a crucial aspect of Site Recovery.

To ensure successful replication, you need to allow outbound access for your VMs to specific URLs. The URLs required for outbound connectivity vary depending on the type of environment you're using.

Here's a list of the required URLs for different environments:

These URLs are required for the Site Recovery service to function correctly.