Azure Site Recovery (Hyper-V to Azure) – Why is a storage account required & how to estimate costs?

Question

Hello,

I am setting up Azure Site Recovery (ASR) to replicate Hyper-V VMs to Azure, and I noticed that during the setup process, a storage account is required.
However, Microsoft documentation indicates that ASR now supports direct replication to managed disks, without the need for intermediate blob storage as you can see in this Q&A (https://learn.microsoft.com/en-us/azure/site-recovery/site-recovery-faq#if-i-replicate-to-azure--what-kind-of-storage-account-or-managed-disk-do-i-need-).

My questions are:

1. Why is a storage account still required when replicating Hyper-V VMs to managed disks?
2. What exactly is stored in this account? Is it only used for replication logs and recovery points, or does it still store full VHD replicas?
3. Is there any official Microsoft documentation that clarifies the exact role of the storage account in ASR for Hyper-V?
4. How should I estimate the costs for implementing ASR for a client? Specifically:
   • How to determine the required storage capacity (e.g., replication logs, snapshots, managed disks, etc.)?
   • Are there any best practices to optimize ASR costs while maintaining a reliable disaster recovery setup for essential workloads?

I want to ensure I fully understand the replication process and have a clear methodology for cost estimation when proposing ASR to clients.

Any insights, official documentation, or cost calculation recommendations would be greatly appreciated!

Thank you in advance!

Answer 1

Hi Killian Jourdan

For Hyper-V machines, Site Recovery creates and uses a storage account for replication. By default, the test failover or failover happens on a storage account. However, it provides an option to failover to managed disks if required. In this case, managed disks are created at the time of failover Cache storage account: The Site Recovery provider software installed on Hyper-V hosts uploads replication data for the VMs configured for replication to a storage account (known as the cache storage account or log storage account) in your subscription. Azure Migrate and Modernize then copies the uploaded replication data from the storage account to the replica-managed disks corresponding to the VM. The cache storage account needs to be specified while configuring replication for a VM

Hyper-V Machines: The cache storage account is in the target that is in Azure charged at General Purpose Storage Account pricing as per the user's selection.

https://azure.microsoft.com/en-us/pricing/calculator/?service=site-recovery For cost You can deploy Hyper-V-deployment-planner-cost-estimation, please find the Link below.

https://learn.microsoft.com/en-us/azure/site-recovery/hyper-v-deployment-planner-cost-estimation

let us know if you have any further queries. I’m happy to assist you further.

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