You can replicate virtual machines by using either array-based replication, vSphere Replication, or a combination of both. You cannot use both replication technologies to protect the same virtual machine.
The following table lists the differences between the two replication technologies and helps you to decide why you must use one technology rather than its alternative.
| Characteristics | Array-Based Replication | vSphere Replication |
|---|---|---|
| Type | Replication using the storage layer. | Replication using the host or vSphere layer. |
| Recovery point objective min or max | 0 up to max supported by vendor. | 5 minutes to 24 hours. |
| Scale | Scales up to 5,000 VMs protected, 2,000 simultaneously recoverable through vCenter and Site Recovery Manager pairing. | Scales up to 2000 VMs (protected and recoverable) through vCenter and Site Recovery Manager pairing. |
| Write-order fidelity | Supports write-order fidelity within and across multiple VMs in the same consistency group. | Supports write-order fidelity on the disks or VMDKs that comprise a VM. Consistency cannot be guaranteed across multiple VMs. |
| Replication level | Replicates at the LUN, VMFS, or NFS volume level. | Replicates at the VM level. |
| Replication configuration | Replication is configured and managed on the storage array. | Replication is configured and managed in the vSphere Web Client. |
| Array and vendor types | Requires same storage replication solution at both sites, for example, EMC RecoverPoint, NetApp vFiler, IBM SVC. | Can support any storage solution at either end including local storage if it is covered by the vSphere HCL. |
| Storage supported | Replication supported on FC, iSCSI, or NFS storage only. | Supports replicating VMs on local, attached, Virtual SAN, FC, iSCSI, or NFS storage. |
| Cost | Replication and snapshot licensing is required. | vSphere Replication is included in vSphere Essentials Plus Kit version 5.1 and later. |
| Deployment | Deployment is fairly involved and must include storage administration and possibly networking. | Deployment requirements are minimal: OVF at each site and start configuring replications. |
| Application consistency | Depending on the array, application consistency might be supported with the addition of agents to the VM. | Supports Volume Shadow Copy Service and Linux file system application consistency. |
| Fault Tolerance (FT) VMs | Can replicate UP FT-protected VMs. After a VM is recovered, it is no longer FT enabled. Does not support FT VMs that are configured for SMP. | Cannot replicate FT-protected VMs. |
| Powered off VMs, templates, linked clones, or ISOs | Can replicate powered off VMs,templates, and linked clones, if all nodes in the snapshot tree are also replicated, and ISOs. | Can replicate only powered on VMs. Cannot replicate powered off VMs, templates, linked clones, ISOs, or any non-VM files. |
| Raw device mapping (RDM) support | Physical and virtual mode RDMs can be replicated. | Only virtual mode RDMs can be replicated. |
| Microsoft Cluster Service (MSCS) support | VMs that are part of a MSCS cluster can be replicated. | Cannot replicate VMs that are part of an MSCS cluster. vSphere Replication cannot replicate disks in multiwriter mode. |
| vApp support | Replicating vApps is supported. | You cannot replicate vApps. You can replicate VMs that are part of a vApp and create a vApp at the recovery site that they are recovered to. |
| vSphere versions supported | Hosts running vSphere 3.5 through 6.x are supported. | Hosts must be running vSphere 5.0 or later. |
| Multiple point-in-time (MPIT) snapshots | MPIT snapshots or rollback is supported by some supported array vendors, for example, EMC RecoverPoint | Supports up to 24 recovery points. |
| Snapshots | Supports replicating VMs with snapshots and maintaining the snapshot tree. | Supports replicating VMs with snapshots. However, the tree is collapsed at the target site. |
| Response to host failure | Replication is not impacted. | Host failure and the VM restarting on another host trigger a full sync. |
