VMware vSphere 5.1 versus Windows Server 2012 Hyper-V: replication

In a  series of postings I will compare VMware vSphere 5.1 and Windows Server 2012 Hyper-V . Goal of the postings is to provide a non-biased overview on features of two main players in the server virtualization market: VMware vSphere and Microsoft Hyper-V.

This posting will give an overview of the replication features of both solutions. Replication is performed for disaster recovery reasons and is meant to provide a faster recovery of data compared to a traditional restore. When a critical component of your infrastructure or the complete datacenter is lost, virtual machines need to be made operational as quickly as possible in an alternative location or on alternative hardware.

Other blogs in the serie are:

Microsoft Windows Server 2012 Hyper-V compared to VMware vSphere 5.1
vSphere 5 versus Windows Server 2012 Hyper-V: storage integration
vSphere 5 versus Windows Server 2012 Hyper-V:management
vSphere 5 versus Windows Server 2012 Hyper-V: high available VMs
vSphere 5 versus Windows Server 2012 Hyper-V: Resource metering for chargeback
vSphere 5 versus Windows Server 2012 Hyper-V: costs
vSphere 5 versus Windows Server 2012 Hyper-V: hybride cloud

Hyper-V Replica

Windows Server 2012 Hyper-V has a free built in feature named Hyper-V Replica. Many of the bloggers with a focus on Hyper-V titled this feature as a Killer feature of Windows Server 2012.

It enables organizations to replicate one or multiple VMs running on Hyper-V hosts to another location. Hyper-V Replica is using a-synchronous replication which means there will always be some data lose in case of failover. The minimum interval of replication is 5 minutes. Hyper-V allows to replicate to multiple locations/sites.

Hyper-V Replica  target is the Small and Medium Enterprises (SME). If you need to replicate dozens or hundreds of VMs you need to look for another solution. I am not aware of any other host based replication solution for Hyper-V so if Hyper-V Replica does not meet requirements, organizations will need to use storage based replication. NetApp has some PowerShell scripting which connects Hyper-V servers to replica LUNs and also software.

Hyper-V Replica code is built into the hypervizor. There is no need to install a specific VM. Installation of Hyper-V Replica is straightforward.  First the Hyper-V Replica Broker role needs to be installed. It needs an IP-address. Thereafter right click the VM which needs to be protected, few clicks and replication is setup.

To prevent an initial transfer of all the virtual machine data over the network (WAN), which will take time and consumes bandwidth, a copy of the virtual machine can be loaded on external media. Then it can be shipped to the recovery datacenter, copied to the Replica server and replication can be started.

During configuration of the replication it is possible to select individual virtual disk files for replication. So a virtual disk holding just the page file is left out of the replication cycle.

Hyper-V Replica allows to store multiple recovery points. This allows to restore to various points in time if for instance the most recent recovery point became corrupted. A maximum of 15 recovery points can be configured.


  • Planned Failover. VMs are shutdown nicely in the protected site and started in the recovery site. Usefull for downtime avoidance for example when a hurricane is approaching or planned maintenance on a major component in the datacenter
  • Test Failover. Usefull for testing the disaster recovery procedure while VMs in protected site are running.
  • Failover. Protected site is unexpectedly lost because of a fire/earthquake/power outage/hard or software fault etc.  VMs needs to be restarted in the recovery site.

If the recovery site uses a different IP-subnet than the protected site Hyper-V Replica is able to inject the new IP-configuration into the VM. This IP-configuration has been configured by the admin during setup of the replication.

Non-disruptive failover testing
Failover can be tested without disturbing the production VMs.

Hyper-V Replica does not have a workflow or runbook which enables an automated, controlled start of VM in case of a failover. When a disaster has happened, the IT-deparment will need to start all VM’s manually in the recovery site. As Hyper-V Replica is targeted at small organizations this should be no problem. Using PowerShell actions can be orchestrated and automated.

When the issue causing the failover has been solved you want to move the VMs from the recovery site back to the protected site. This is an easy operation for Hyper-V Replica. Just a few mouseclicks.

Application consistent
Replication of data is not enough. What is important is : can the replicated data be used? Is is consistent, will a database start after a failover? Hyper-V Replica uses VSS snapshots which makes sure databases supporting VSS are put in a consistent state when replication is done.

Hyper-V Replica can be extended with functionality by using PowerShell scripts.

Recovery infrastructure
Replication software needs obviously an infrastructrure in a recovery site. As operating a recovery site purely for DR reasons costs a lot of money, Service Providers are starting to offer Disaster Recovery as a Service. Using DRaaS there is no need to operate or own two datacenters (protected and recovery). However I am not aware of Service Providers which support Hyper-V Replica yet. This will be a matter of time.
Hyper-V Replica is ready for replication to a Service Provider. Replication authentication can be done using X509 certificates.

Mind it is not possible to backup the VMs running in the recovery site using DPM. A reason for which the replica VMs are backuped not in the protected site but in the recovery site would be to prevent stressing the VMs in the protected site. Another reason would be to prevent having the backup data in the protected site. So when Hyper-V Replica is used, DPM needs to backup the VMs in the protected site. Then the DPM backup reposity will needs to be replicated to the recovery site as well. See this Microsoft posting for the details.

Alternative solutions
I am not aware of many *other* Disaster Recovery tool for Windows Server 2012 Hyper-V which is able to replicate on host level and/or storage level, orchestrate storage replication , orchestrate test and failover, perform automated failback and is able to do non-disruptive testing.

NetApp SnapManager for Hyper-V has features for DR. Not sure if this can do runbooks and orchestration.

More info
Thomas Maurer has a lot more info on Hyper-V Replica (and on other Hyper-V and System Center subjects as well)
Aidan Finn has a good posting as well if you do not mind the bias and VMware bashing.
Microsoft has a lot of documents on Hyper-V Replica here.

VMware vSphere Replication

VMware vSphere Replication was introduced as  part of VMware Site Recovery Manager (SRM) with the introduction of vSphere 5. At that time SRM did not support the vSphere Essentials and Essentials Plus editions. These editions are limited to 3 hosts with 2 CPUs each and are targeted at the SMB market.
VMware announced at VMworld 2012 that its host based replication software named vSphere Replication will be included free in the vSphere Essentials Plus, Standard, Enterprise and Enterprise Plus editions of vSphere 5.1. So vSphere Replication is unbundled from SRM.

Is is very likely VMware decided to include vSphere Replication as a free feature because Microsoft had the Hyper-V Replica feature for free.

The vSphere Replication framework consists of a vSphere Replication appliance that is paired with a single
vCenter server. This appliance provides the management framework for vSphere Replication and also acts as the
target for replicated blocks. Increased scale or remote sites managed by a single vCenter server might lead to
the choice of deploying up to 10 vSphere Replication Server (VR Server) virtual appliances. The VR server
appliances function strictly as a destination target for replication and enable simple scaling and distribution of
the replication framework. As many as 500 virtual machines can be protected with an individual vSphere
Replication instance.

Need for an additional vCenter Server license.

Depending the infrastructure one or two vCenter Server licenses are needed to use vSphere Replication.
For a remote office/branch office of which its local ESXi servers are managed by a central vCenter Server (located in the main datacenter/HQ) no additional vCenter Server license is needed. In this case the recovery location is the main datacenter.

For a standalone office with a local vCenter Server, an additional vCenter Server is needed for the recovery location. This makes the vSphere Replication option more expensive than Hyper-V Replica.


vSphere Replication allows to replicate individual VMs to another site. Replication is storage agnostic and works on any vSphere supported storage platform.  It can only replicate VMs which are turned on. Templates are not replicated. It can be configured to replicate at the most each 15 minutes to 24 hours. This means in case the VMs is lost 15 minutes of data will be lost in the replica VM.

New in version 5.1 is the ability to replicate Raw Device Mapping disks (RDM) in virtual compatibilty mode.

vApps are not supported. Admins will need to manually protect or de-protect each VM part of a vApp.

To prevent large datatransfers when a VM is enabled for protection data can be copied to a removeable devices, shipped to the recovery datacenter and installed. Then changes will be replicated over the network.

vSphere Replication part of vSphere is limited to replication of a maximum of 500 VMs. Organization which require to replicate more VMs will need to buy Site Recovery Manager or a third party solution.

Just like Hyper-V Replica, vSphere Replication does not have an orchestration function. VMs will need to be manually connected to the network and manually started by IT-staff after a failover.  vSphere Replication does not have the ability to automatically change the IP-address of the VM. Using PowerShell this can be automated.

Non-disruptive failover testing
The replica cannot be powered on and recovered if the original virtual machine is still reachable and is itself still
powered on. To continue, the primary copy of the virtual machine must be unreachable by vCenter Server or powered off.
As it is not likely the primary VM can be switched off I guess this means the WAN-connection between the vSphere Replication server in the recovery site and vSphere Replication Server in protected site must somehow be disconnected.

Application consistent
Automatic integration with Microsoft’s Volume Shadow Copy Service (VSS) ensures that applications such as Microsoft Exchange or Microsoft SQL Server databases are quiescent and consistent when replica data is being generated. A very quick call to the virtual machine’s VSS layer flushes the database writers for an instant to ensure that the data replicated is static and fully recoverable.

When the protected site is recovered it is likely that you want the VM running in the recovery site to be moved to the protected site again. However vSphere Replication does not offer an easy failback. You will need to start over again setting up protection per VM.

Recovery infrastructure
Quite a few service providers already support VMware Site Recovery Manager. I suspect they also or soon will support vSphere Replication. So you could use their Disaster Recovery as a Service instead of having to buy/lease your own datacenter and equipment.

Alternative solutions
There are quite a few alternative solutions if vSphere Replication does not meet requirements.
VMware Site Recovery Manager does orchestration of storage level replication, does host based replication,can be used for 100s of VMs, does runbooks,  and lots more.

Zerto Virtual Replication does host based replication. Lots of good features. For a compare of vSphere Replication versus Zerto Virtual Replication see this blog titled  vSphere Replication and Zerto – What’s the Difference?

VirtualSharp ReliableDR goes one step further. It does not only replicate, but also verify the replicated data is useable. They have a free edition available and a paid edition. See my blog on the free edition which was released at VMworld 2012.

For a compare of the three solutions (based on earlier versions) see my posting titled Overview of disaster recovery solutions for VMware vSphere

More info
More info on vSphere Replication here.

Hyper-V Replica has all the features Small and Medium Businesses need for disaster recovery. As soon as service providers offer a DRaaS service , Hyper-V Replica is a very cost effective solution for DR.

vSphere Replication is a very basic data protection tool by enabling replication. Some critical features are missing.

The table below shows a summary of features mentioned in this blog.

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