Reduce the amount of network traffic and time during the initial full synchronization. You can copy the virtual disk files in the target datastore and using them as replication seeds.

When you configure a replication for the first time, vSphere Replication performs an initial full synchronization of the virtual machine’s disk. This operation is network and time intensive.

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

Note: To effectively reduce the amount of network traffic and time during the initial full synchronization, and to replicate only the changed blocks, you must upgrade both sites to vSphere Replication version 8.7 and ESXi host version 8.0. If one of the sites (the source or the target) runs vSphere Replication version 8.7 and ESXi host version 8.0, and the other site operates with previous versions of vSphere Replication and the ESXi host, all disk blocks will be replicated, and not only those that were changed.

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.

Using vSphere CLI for Storage Operations

To create a copy of a virtual disk, you can use the vSphere CLI to manage VMFS volumes, vmkfstools.

To prevent performance and data management issues on ESXi hosts, avoid using standard Linux commands for storage operations.

For more information, see https://docs.vmware.com/en/VMware-vSphere/6.7/com.vmware.vsphere.storage.doc/GUID-01D3CF47-A84A-4988-8103-A0487D6441AA.html.