VM replicas

The VM replica feature provides a quick way to recover a failed VMware VM. It creates a virtual machine replica of the original VM, then keeps this replica up-to-date by applying backups of the original VM as they run. In the event of a disaster, you can bring this replica online to immediately assume the role of the failed VM. You can use the replica to replace the original VM temporarily or use it as a permanent replacement.

To use the feature, simply set up the replica by using the Create Replica VMs dialog. The appliance then creates the replica from the most recent backup of the original VM, and automatically applies all subsequent backups. Because the replica is continually updated, it is ready for production use at any time.

While creating the replica, you specify the ESXi host location where the replica VM will reside. The replica VM is created as a cold stand-by in the specified location. The replica is powered off and has no network connectivity. Because the replica remains powered off even as backups are applied, it consumes no compute resources.

After the first backup has been applied, replica creation is complete. You can then do the following as needed:

●   Audit the replica to verify the integrity of the machine and its data and applications. In audit mode, the replica runs on a private network (inaccessible from the production network). This enables you to check the replica VM while the original VM is still operating in production. It is recommended that you periodically audit the replica to ensure it functions as expected.

●   Bring the replica into live mode to assume the role of the original VM. Once the replica has booted into live mode, simply configure network settings to bring the VM online in your production environment. Live mode is intended as a temporary solution. You should exit live mode (by tearing down the replica) as soon as you have verified that the live replica is functioning as expected in production. (You can keep using the replica VM after it exits live mode by selecting the Delete the VM replica from the appliance only option in the Tear Down VM replica dialog. For considerations, see Live mode recommendations.)

See the following topics for details on using the VM replicas feature:

●   Replica restore jobs

●   VM replica requirements

●   Creating VM replicas

●   Working with VM replicas

Replica restore jobs

To keep a replica up-to-date, the appliance automatically queues a replica restore job each time a backup successfully completes. The restore job runs as soon as possible to apply the backup to the replica. (For example, the job cannot run if the replica is in audit mode or if the job is queued behind other active jobs.)

The restore job applies the backup to the replica VM and then consolidates VM snapshots. During the restore, the replica is in restore mode and the replica restore job displays on the Active Jobs tab:

NOTE  Do not cancel a replica restore job by clicking Cancel on the Active Jobs tab. Instead, bring the replica into audit mode to temporarily stop applying backups. (For details, see Do not cancel an active replica restore job.)

Entering live mode while a restore is in progress

Beginning in release 10.1.2, the replica can quickly enter live mode while a restore is in progress. The appliance boots the VM into live mode immediately and cancels the running replica restore job. Upon entering live mode, the replica is marked invalid because the replica role no longer applies. After configuring network settings for the live replica VM and verifying that it is functioning as expected in production, you tear down the replica on the Unitrends appliance. You can then opt to create a new replica for the live VM.

Entering audit mode while a restore is in progress

Beginning in release 10.1.2, the replica can quickly enter audit mode while a restore is in progress. The appliance boots the VM into audit mode immediately and cancels the running replica restore job. See these topics for details:

If the restore job did not finish applying the backup to the replica:

●   The canceled replica restore job moves to Error status on the Active Jobs tab:

●   The canceled replica restore job displays in Failure status on the Replicas Report. Click the job to view details in the Replica History Status dialog. Details contain the message Canceled and failed. Next replica restore will retry:

●   The canceled job remains in the replica backlog. When the replica exits audit mode, the appliance queues a new restore job to replace the one that was canceled.

If the restore job finished applying the backup to the replica:

●   The canceled replica restore job moves to Warning status on the Active Jobs tab:

●   The canceled replica restore job displays in Warning status on the Replicas Report. Click the job to view details in the Replica History Status dialog. Details contain the message Canceled but successful. Some cleanup may occur on the next replica restore:

●   If needed, snapshot consolidation for the canceled job is performed during the next replica restore. Note that the next restore may take extra time. Do not interrupt the next restore. Repeatedly interrupting restore jobs significantly degrades performance.

Do not cancel an active replica restore job. Instead, bring the replica into audit mode.

Each successful backup of the original VM is applied to the replica as soon as the backup completes. The appliance applies the backup by running a replica restore job, which displays on the Active Jobs tab as shown here:

If you cancel a replica restore job by using the Cancel button on the Active Jobs page, the replica may become invalid and need to be recreated (for details, see Halted mode in VM replica modes). To temporarily stop applying backups, bring the replica into audit mode instead (as described in Working with VM replicas). Use the procedure To exit audit mode to start applying backups again. Note that all backups that ran while the replica was in audit mode will be applied to the replica upon exiting audit mode. You cannot skip applying a specific backup to a replica.