Azure Site Recovery: Preview version vs Classic version

Azure Site Recovery is one of the most useful Azure tools to setup the server DR solution between on-promise and Azure. It replicates workloads running on physical and virtual machines (VMs) from a primary site (mostly on-promise) to Azure. When an outage occurs at primary site, the on-promise VM can be failed over to Azure and access servers and apps from there.

In August 31, 2021, Azure released a Public Preview of a new Azure Site Recovery version (Preview version). This post is to list the key differences the Preview versions and Classic version for quick readers.

What you need to know if you do not want to continue to read:

  • When you create a new Recovery Service Vault in Azure, the Preview version will be the default and recommended settings. You can switch back to Classic version, but you cannot revert it back post the switch, re-create the Recovery Service Vault is the only approach then.
  • The Preview version do not support “Private Links” at the time of writing this post, which means you cannot use your private endpoints by VPN or ExpressRoute to replicate the data from on-promise to Azure.
  • There are different FW requirements between Preview version and Classic version because some Azure Site Recovery components are offloaded from on-promise to Azure. Need to review the Azure document carefully about the differences.

Architect difference between Preview version and Classic version

In Classic version,

when deploy the on-promise Azure Site Recovery appliances, you need to plan below roles.

  • Configuration server – The configuration server coordinates communications between on-premises and Azure and manages data replication.
  • Process server – The process server acts as a replication gateway. It receives replication data; optimizes it with caching, compression, and encryption, and sends it to a cache storage account in Azure. You can have multiple process servers to adapt the workload.
  • Master target server – The master target server handles replication data during failback from Azure.

All these roles can be deployed into a single appliance/Windows server or separated ones, depends on the data replication workload. Therefore, there is a bit design consideration.

In addition, since a configuration database is installed in the configuration server, a regularly configuration server backup is required at the on-promise site.

In Preview version,

The on-promise Azure Site Recovery appliances are stateless and all its components have been converted into micro-services which are hosted on Azure. Therefore, there is no need to perform complex design, just simply deploy an Azure Site Recovery appliance in the on-promise environment to start.  

The stateless appliance also means there is no need to back up the appliance anymore. Just re-deploy a new appliance if the running appliance is crashed. Same for scaling, simply deploy additional new appliances and add them into the Recovery Services vault.

New Feature in Preview version:

Automatic Upgrade – configuration server components and mobility services can be automatically updated, and it is triggered at 12:00 AM local time every day if a new version is available.  This setting is enabled by default and can be switched off.


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