the VM’s replication set without requiring the entire replication relationship to be re-
created. Instead, the Set-VMReplication cmdlet is used with the -ReplicatedDisks
argument, which can specify the disks that should be replicated. For example, to add
all disks to the replication set, you could use the following:
Set-VMReplication -VMName
-ReplicatedDisks (Get-VMHardDiskDrive -VMName
One key point of Hyper-V Replica is that a virtual machine can have only one replica.
Additionally, in Windows Server 2012 and above, you cannot create a replica of a
replica VM, known as extended replication. This is not a problem if you consider the
original goal of Hyper-V Replica, which is having a replica of a virtual machine in a
disaster-recovery location. This is also why the fixed interval of 5 minutes was a good
default value.
But some organizations used Hyper-V Replica differently. They used Hyper-V Replica
within a single datacenter where they could not use clustering or did not want to use
it. This is also the reason the 5-minute replication frequency was too restrictive and
organizations wanted to replicate more frequently. These same organizations still
wanted to be able to have a replica to an alternate site, which required extending
replication. As mentioned, the ability to add a replica to the existing replica virtual
machine was added in Windows Server 2012 R2. Note you still cannot have more than
one replica for a single VM; so, with Windows Server 2012 R2 and above, the primary
virtual machine can still have only one replica, but that replica can now have its own
replica, as shown in Figure 8.4.
Figure 8.4 Windows Server 2012 R2 Hyper-V extended replication
Note that an extended replica can be used in any situation, not just if you have the
main replication within a datacenter. If you have two DR locations, the Hyper-V
extended replica can be beneficial. I’ve also seen it when in the primary datacenter the
standard Hyper-V Replica feature is used to replicate a virtual machine from one