VM replica requirements

The following requirements must be met to use the VM replica feature:

Requirement

Description

Unitrends appliance

The Unitrends appliance used to create the VM replica must meet these requirements:

• Must be running version 10.1 or higher.
• Must be the backup appliance that is protecting the original VM or the target appliance that is receiving copies of the original VM's backups.
• License Feature String must contain MKT=2 or higher. To add this feature, contact your Sales Representative.

Host-level backup or hot backup copy

A successful host-level backup or host-level hot backup copy of a VMware virtual machine is required to create the replica VM. (Hyper-V, AHV, and XenServer VMs are not yet supported).

The replica VM is kept up to date by applying subsequent backups as they run. Be sure to capture changes on the original VM by running backups at regular intervals.

Notes:   

• The replica VM is based on the latest backup or hot copy of the virtual machine. The replica VM does not include any VM disks that were excluded from the backup.
• If no backup or hot copy exists, you can still set up the replica by running the create replica procedure. In this case, the appliance creates a "shell" replica in uninitialized(pending: create) mode. The replica remains in this mode until a successful VM backup or hot backup copy is created. (An uninitialized replica cannot assume the role of a failed VM. At least one backup must be applied before the replica can replace the original VM.)

Hypervisor version

The ESXi server that hosts the replica VM must meet these requirements:

• Must be running a paid ESXi 5.0 or a higher version listed in the Compatibility and Interoperability Matrix.
• Essentials and Essentials Plus editions are supported for ESXi servers that are managed by a vCenter only. (Essentials and Essentials Plus editions running on stand-alone ESXi servers are not supported.)
• Must support the operating system (OS) of the VM. (See the VMware documentation for details.) For example, a replica of a Windows 2016 VM cannot reside on an ESXi 5.1 host.
• Can be the host where the original VM resides or an alternate host running the same software version as the original or a later version.

Virtual host asset

The ESXi server must be added to the appliance as an asset. See Adding a virtual host for details.

One replica per VM

An appliance can create only one replica for each virtual machine instance. To create another replica for a given VM, you must first tear down any existing replica. If you retain the replica VM on the hypervisor during teardown, you can create another as long as you specify a different replica name.

Compute and storage

The ESXi server that hosts the replica must have adequate compute and storage resources:

• The replica's compute resources (processors and memory) match those of the original VM.
• The replica's virtual disks are based on the original VM, but are always thin provisioned. Any virtual-mode raw device mapping (RDM) disks recover as standard virtual disks.
• The maximum disk size is capped by what the hypervisor supports. For VMs with disks larger than 2 TB, the ESXi server must be running ESXi 5.5 or a higher version listed in the Compatibility and Interoperability Matrix.

If the virtual host does not have or support the specified resources, the replica cannot be created and an error displays in the Create Replica VMs dialog.

Notes:   

• The replica VM is created as a cold standby. No compute resources are used until you boot the replica in live or audit mode.
• Once you create the replica, you can edit its compute resource settings as needed. For details, see Working with VM replicas.

Replica VM hardware version

The replica VM is configured with the highest hardware version that the hypervisor supports.

Replica VM changeability

Once you have created the replica, do not make any changes to the replica VM outside of the Edit VM Replica Details dialog. Any alteration to the replica VM may invalidate the replica.

Notes:   

• If the replica becomes invalid due to VM configuration changes made outside of the Edit VM Replica Details dialog, it enters halted mode and can no longer be used. You must delete the halted replica and create a new one.
• When a replica enters live mode, it becomes invalid because the replica role is no longer applicable. You can make changes to a live replica VM by using the ESXi hypervisor.

Appliance DR limitation

Appliance disaster recovery does not recover VM replicas. You must set up new replicas after you recover the appliance.