Product : Microsoft, Azure Site Recovery/UR40, x86
Feature : Replication Method, Architecture, Design & Deploy
Content Owner:  Herman Rutten
Log-based CBT (VMware/Hyper-V/Physical)
Snapshot-based (Azure IaaS)
VMware vSphere / Physical Servers: The ASR Process Server writes replication logs to a cache storage account in the Azure target region. For every protected disk, log data is replicated to a Managed Disk in Azure. This disk has the prefix of asrseeddisk. It stores the copy of protected disk and all the recovery point snapshots.

Microsoft Hyper-V: The Hyper-V Replica Replication Tracker (HRRT) tracks all changes as Hyper-V replication logs (.hrl). These log files are located in the same folder as the disks. Each disk has an associated .hrl file that is sent to the end-user organizations Azure Storage Account on delta replication. When a log is in transit to Azure, the changes in the primary disk are tracked in another log file, in the same folder.

Azure IaaS: Recovery points are created from snapshots, and stored in accordance with retention settings in the replication policy. ASR takes crash-consistent snapshots of data by default, and app consistent snapshots if you specify a frequency for them.

CBT = Changed Block Tracking