Performing an Offline Full Synchronization of a Virtual Machine Between Two Sites Using vSphere Replication

Products

• VMware vSphere ESX 8.x
• VMware vSphere ESX 7.x
• VMware vSphere ESXi

Issue/Introduction

• When deploying virtual machines across geographically separated sites, performing a standard online full synchronization via vSphere Replication can be severely bottlenecked by network constraints.
• This article provides a step-by-step guide to perform an offline full synchronization (seeding) of a virtual machine between two vCenters.
• This process overcomes network bandwidth and latency constraints by taking an offline copy from the source VM, importing it into the destination vCenter, and re-configuring vSphere Replication using seed files.

Environment

• VMware vSphere 7.x
• VMware vSphere 8.x
  
  
• VMware vSphere Replication 7.x
• VMware vSphere Replication 8.x

Cause

High network latency and limited bandwidth between two remote sites make a standard online full synchronization of a large virtual machine impractical or prone to timeouts and failures.

Resolution

To successfully configure vSphere Replication using offline seeding, follow these recommended steps:

1. Power off the source VM to ensure data consistency and prevent any changes during the export process.

2. Export or manually copy the source VM's virtual disk files (.vmdk) to portable storage or directly to the destination datastore using out-of-band methods.

3. Place the copied .vmdk files into the designated target datastore folder where the replica VM will reside.

4. Launch the vSphere Replication configuration wizard for the virtual machine.

5. Select the Select seeds option during the wizard, browse to the manually copied files on the destination datastore, and complete the setup.

6. Let vSphere Replication perform a checksum calculation to verify the files and synchronize only the accumulated delta changes.

Additional Information

 

• Data Consistency: Always ensure the source virtual machine is powered off or in a quiescent state (using quiesced snapshots if applicable) before copying the .vmdk files to guarantee that the seed data is consistent.

• Checksum Phase: The initial checksum process can take some time depending on the size of the virtual disks, but it processes locally at the target site without heavily consuming WAN bandwidth.

• Naming Conventions: Ensure that the folder structure and virtual disk names at the target destination match what vSphere Replication expects during the configuration wizard.