Azure Site Recovery Replication

Azure Site Recovery (ASR) is a disaster recovery service that replicates workloads from a primary location to a secondary location, enabling failover if the primary becomes unavailable. Unlike Azure Backup (which creates point-in-time recovery points), ASR maintains a continuously updated replica of your VMs so you can fail over with minimal data loss. ASR supports Azure-to-Azure replication, on-premises VMware or Hyper-V to Azure, and physical servers to Azure.

For Azure-to-Azure replication, ASR uses the Mobility Service (installed automatically as a VM extension) to capture write I/O from the source VM's disks. The captured data is transmitted over the Azure backbone to a cache storage account in the target region, then written to replica managed disks. A Recovery Services vault in the target region orchestrates the replication. The source VM continues running normally during replication — there is no performance impact for writes below the replication bandwidth.