Versions of VMware Site Recover Manager (SRM) prior to version 5 required array-based replication and a VMware-certified Storage Replication Adapter to be installed in order to function.  SRM itself did not perform replication.

VMware SRM 5 now includes an optional replication feature with the following characteristics:

• vSphere Replication (VR) is included with SRM 5 for free but array-based replication is still supported
• VR offers a cost-effective means of protecting 2^nd and 3^rd tier applications  and remote offices
• VR is not intended to replace SAN-based replication for mission-critical applications
• VR requires version 5 of vCenter and SRM but ESX host versions can vary

Additional VR Characteristics:

• Adds native replication to SRM
• Replication is enabled per VM, not per datastore, and can include some or all of the VM’s disks
• VMs can be replicated regardless of the underlying storage – even to or from local storage on a host!
• Supports Microsoft VSS for guest OS quiescing
• Initial copy of VM can be seeded by online replication or by transporting external media
• Replicated disks can be placed anywhere at the recovery site
• Replication is managed via the vCenter console
• Changes on the source disk are tracked by ESXi and only deltas are sent to the remote site
• Replication does not use VMware snapshots – very nice!
• RPO is configurable between 15 minutes and 24 hours

VR Limitations:

• Focus is on virtual disks of powered-on VMs
• VR works at the virtual device layer
• FT, linked clone, templates not supported
• Automated fallback of VMs not supported in the initial release
• Virtual hardware 7 or later required in VM

VR Use Cases:

• Site-to-site (async) for SMB customers where no SAN replication is available
• Alongside array replication (compliments rather than replaces)
• Remote offices to existing paired SRM datacenters in a hub & spoke model
• DR as a Service (DRaaS) provider model, eliminating the need for a dedicated customer-owned secondary site up to a 10:1 ratio
• Planned VM migration between sites