I have previously written a post (link below) about how Availability Zones are beneficial for cloud resource redundancy. Availability Zones provide high availability within a single Azure region by isolating workloads across physically separate datacenters.
However, Availability Zones only address intra-region resilience. So what happens if an entire region becomes unavailable?
This is where a robust disaster recovery (DR) strategy becomes essential and where Azure Site Recovery comes into the mix.
Azure Site Recovery (ASR) is Microsoft’s disaster recovery solution that enables you to replicate workloads from one region to another, ensuring business continuity during major outages.
ASR continuously replicates your virtual machines (VMs) and other supported workloads to a secondary region. In the event of a disaster, you can quickly initiate a failover to bring your applications online in the recovery region.
This capability transforms your DR strategy from manual, time-consuming recovery into a controlled, orchestrated, and automated process.
Main benefits to Azure Site Recovery
Azure Site Recovery provides several advantages for organisations looking to strengthen their resilience:
- Regional disaster protection – Protects against full regional outages by replicating workloads elsewhere.
- Minimal downtime – Enables rapid failover with low Recovery Time Objectives (RTO).
- Data protection – Supports configurable Recovery Point Objectives (RPO) to minimise data loss.
- Non-disruptive testing – Run test failovers without impacting production.
- Orchestration – Use recovery plans to automate complex failover sequences across multiple VMs.
ASR recommendations
When implementing ASR, there are a few best practices worth following.
1. Use a Dedicated Recovery Services Vault
I recommend using a separate Recovery Services Vault specifically for Azure Site Recovery.
This approach provides:
- Separation between backup data and replication data
- More granular control over security and access policies
- Cleaner management and visibility of your DR configuration
Having distinct vaults for Azure backup and ASR ensures that operational tasks and policies remain clearly defined and reduces the risk of accidental misconfiguration.
2. Place the vault in the target recovery region
Another important recommendation is to deploy the Recovery Services Vault in the target (failover) region.
This ensures:
- Metadata and configuration data remain accessible even if the primary region is unavailable
- Faster recovery coordination during an outage
- Improved resilience of the ASR control plane
In a true regional disaster scenario, having all recovery orchestration components in the secondary region is very important for a successful recovery.
3. Plan your network in advance
Networking is often overlooked but is important in a failover scenario.
You should:
- Ensure connectivity to the virtual networks (VNETs) in the recovery region is configured prior to needing the DR environment. This will help to reduce recovery time during the worst poosible time.
- ASR will create VNETs in the failover region with matching IP address space. So, you need to ensure that connectivity to the failover region is only available when you require it, to avoid any network conflicts outside of a DR situation.
- Configure Network Security Groups (NSGs) and routing rules as required.
- Consider your DNS failover strategy (e.g. Azure Traffic Manager or Azure DNS).
Proper planning ensures your applications come online seamlessly during failover with as little last-minute fixes as possible.
Understanding failover options available in ASR
ASR provides multiple types of failover, each serving a different purpose:
- Test Failover – allows you to validate your DR strategy without impacting production workloads.
- Planned Failover – used during controlled scenarios (e.g. maintenance), typically with zero data loss.
- Unplanned Failover – triggered during an outage, prioritising rapid recovery over zero data loss.
Additionally, once the primary region is restored, you can perform a failback to return workloads to their original location.
Cost considerations
Azure Site Recovery uses a simple pricing model:
- A single monthly fee per protected VM
- Storage costs for replicated data
- Networking costs during replication and failover
At the time of writing, the ASR licensing cost is approximately £19.80 per VM per month in the UK South region.
Although there are additional storage and bandwidth costs, ASR is often significantly more cost-effective than maintaining a fully active secondary environment.
Common use cases
Azure Site Recovery is typically used in scenarios such as:
- Business-critical applications requiring high availability
- Compliance-driven disaster recovery requirements
- Migration of on-premises workloads to Azure
- Protection of legacy systems without built-in redundancy
Final thoughts
Availability Zones play an important role in protecting applications within a region, but they are not a complete disaster recovery solution.
Azure Site Recovery fills this gap by enabling cross-region replication and recovery, ensuring that your workloads remain available even in large-scale outages.
By implementing ASR with best practices such as:
- Dedicated recovery services vaults (RSVs)
- Strategic region placement
- Proper network planning
You can significantly improve your organisation’s resilience and readiness for unexpected incidents.
If you’re building a cloud strategy in Azure, ASR shouldn’t be an afterthought, it should be a core component of your disaster recovery design in my opinion.
Hope this helps and thanks for reading!
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