When Performing a replication using Veeam Backup, the data is transferred over SCP.  Veeam utilizes it's FastSCP functionality to transfer the data directly from the VCB Proxy to the Target Host, or if not using VCB, directly  from Source to Target Host.

After the initial full replication, only changes are sent across the wire for all subsequent replications.  Using Veeam's synthetic technology, the target VMDK(s) is updated with these changes so the replica on the target is in a ready to start state.

Michael,

The "scan" is actually much faster than that, it's based on hashing algorithms at the block level, not a direct block by block comparison of the previous backup.  The "scan" is done either by the VCB proxy or on the ESX host and does not have to come back through the Veeam Backup server. Any empty blocks (0 bytes) are not transfered but will be included in the target VM.  For instance, if you have 100 GB pre-allocated VMDK but are only using 30GB then only 30 GB will be transferred.

We have customers replicating multi-gigabyte VM's every 30 minutes.  Of course, there are many factors involved, especially network speed if you're replicating off-site so performance may vary.

Thanks,

-doug