You can reduce the network traffic that data transfer generates during the initial full synchronization. vSphere Replication allows you to copy virtual disk files or use existing files in the target datastore, and point the files as replication seeds when you configure a replication.

vSphere Replication compares the differences on the source and target site, and replicates only the changed blocks.

When, during replication configuration, you select a target datastore for the virtual machine or a specific disk, vSphere Replication looks for disks with the same filename in the target datastore. If a file with the same name exists, a warning appears in the wizard. You can review and configure the replication seeds or choose not to use any replication seeds. If you choose not to use the discovered seeds, then replica files are placed in a new directory with a unique name. If you choose to configure seeds by selecting the Select seeds check box, then a new page appears in the wizard where you can configure seeds for each disk on each virtual machine.

Note: If you plan to copy files from the source to the target datastore, the source virtual machine must be powered off before downloading the VMDK files that will be used as seeds for the replication.

To prevent performance and data management issues on ESXi hosts, avoid using standard Linux commands for storage operations. You can use the vSphere CLI to manage VMFS volumes, vmkfstools.

For more information, see the VMware knowledge base article at https://kb.vmware.com/s/article/900.