UPDATE: a new article has been published that supersedes this one. If you have reached this page through a search or bookmark, then read the following article instead:
SRM supports two different replication technologies, Storage Array or Array-Based Replication and vSphere Replication. One of the key decisions when implementing SRM is which technology to use and for what VMs. The two technologies can be used together in an SRM environment though not to protect the same VM. Given that, what are the differences and why would you use one over the other? This table will provide all the answers you need:
Array-Based Replication
vSphere Replication
Type
Replication using the storage layer
Replication using the host/vSphere layer
RPO min/max
0 up to max supported by vendor
15 mins to 24 hours
Scale
Scales up to 5,000 VMs protected/2,000 simultaneously recoverable per vCenter/SRM pair
Scales up to 2,000 VMs (protected & recoverable) per vCenter/SRM pair
Write order fidelity
Supports write order fidelity within and across multiple VMs in the same consistency group
Supports write order fidelity on the disks/VMDKs that make up 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/ vendor types
Requires same storage replication solution at both sites (eg. EMC RecoverPoint, NetApp vFiler, IBM SVC, etc)
Can support any storage solution at either end including local storage as long as it is covered by the vSphere HCL
Storage supported
Replication supported on FC, iSCSI or NFS storage only
Supports replicating VMs on local, attached, VSAN, FC, iSCSI or NFS storage
Cost
Replication and snapshot licensing is required
vSphere Replication is included in vSphere Essentials Plus 5.1 and higher
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 may be supported with the addition of agents to the VM
Supports VSS & Linux file system application consistency
FT VMs
Can replicate UP FT protected VMs (once recovered VM is no longer FT enabled). Does not support SMP FT VMs.
Cannot replicate FT protected VMs
Powered off VMs/Templates/Linked clones/ISO’s
Able to replicate powered off VMs, Templates, Linked Clones (as long as all nodes in the snapshot tree are replicated as well) and ISOs
Can only replicate powered on VMs. Cannot replicate powered off VMs, Templates, Linked Clones, ISOs or any non-VM files
RDM support
Physical and Virtual mode RDMs can be replicated
Only Virtual mode RDMs can be replicated
MSCS support
VMs that are part of a MSCS cluster can be replicated
Cannot replicate VMs that are part of a MSCS cluster. VR cannot replicate disks in multi-writer mode.
vApp support
Replicating vApps is supported
Replicating vApps is not possible. However, it is possible to replicate VMs that are part of a vApp and to create a vApp at the recovery site that they are recovered into
vSphere versions supported
Hosts running vSphere 3.5-6.0 are supported
Hosts must be running vSphere 5.0 or higher
MPIT
Multiple point in time snapshots or rollback is supported by some supported array vendors (eg. 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 triggers a full sync. For details about what a full sync involves see the vSphere Replication FAQ
If you want more information on supported array-based replication vendors and compatibility check out the VMware Compatibility Guide. The vendor for the array you have or are interested in is also a great source for information. Reading the release notes for your SRA is highly recommended.
For detailed information on vSphere Replication including answers to commonly asked questions check out the vSphere Replication FAQ
