VMware Replication Using VAIO (Live Sync I/O)

vSphere APIs for I/O Filtering (VAIO) is a framework that enables block-level replication of virtual machine data. The Live Sync I/O feature uses block-level replication to synchronize block devices or virtual machine disks, continuously streaming updates from source to destination VMs. Each source VM and the resulting destination VM is a replication pair.

Block-level replication provides the following benefits:

  • Eliminates the need to take and clean up snapshots frequently on the source VM, reducing the I/O impact on the production system.

  • Enables more frequent and granular updates and synchronization between source and destination VMs, making it possible to meet reduced recovery time objectives (RTOs) and recovery point objectives (RPOs) for virtual machines.

  • Provides a dynamically pruned history of recovery points without running backups or relying on synthetic full backups to consolidate incremental updates for different points in time.

You can configure and run Live Sync I/O from Command Center or the CommCell Console.

After you configure block-level replication, backup and replication begins automatically. The backup of the source VM provides the initial image for the creation of the destination VM. Replication is automatically enabled to capture subsequent updates to the source VM.


Live Sync I/O is supported only from streaming backups. It is not supported from IntelliSnap backups.

Recovery Points

Recovery points are crash consistent copies of volumes on the destination VM that match the data that was written on the source VM volumes at a specific point in time.

Application-consistent backups that are performed with the assistance of application agents or by performing VSA backups create application-consistent recovery points (ACRPs).

ACRPs are based on application-consistent VM snapshots. If a replication pair is configured for ACRPs, the replication service periodically creates temporary application-consistent snapshots on the source VM. The Recovery Point Store (RP Store) on the destination site records ACRPs as point-in-time recovery points.