5 1 0:Hyper-V Backup with Resilient Change Tracking (RCT)

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Resilient change tracking (RCT) enables change block tracking capability for Hyper-V VM disks. At the data block level, RCT tracks changes to a VM disk (VHDX) that occur in between backup operations and only blocks that have changed since the last backup are backed up. This approach is more efficient and can significantly reduce space consumption when you have multiple snapshots on a single host.

How it works

SEP sesam uses resilient change tracking (RCT) for Hyper-V backups on Windows Server ≥ 2016 (Hyper-V VM ≥ 6.2) by default.

During a full backup of a virtual machine, a snapshot is created of the VM disk. The snapshot contents are backed up and snapshot is deleted automatically after backup is successfully completed. SEP sesam creates a meta file for Hyper-V RCT backup in /var/work directory, where the information about RCT and VMs is stored.

During the next backup a new snapshot is created and verified against the RCT change-tracking information to determine what data has changed. Only the changed blocks are backed up. After the snapshot is converted to a reference point (merged with the VM by Hyper-V), the differencing file (.avhdx) is deleted automatically.

Any manually created snapshots do not affect the backup chain that is created by the RCT process.


To ensure error-free operation of SEP sesam and to improve performance, make sure that the following conditions are met for backing up the Hyper-V virtual machines with RCT:

  • RCT is available on Windows Server 2016 and later.
  • The functionality is available in SEP sesam version Jaglion V2.
  • Only VHDX files are supported for Hyper-V RCT. VHD files are not supported and can be converted to VHDX files by Hyper-V Manager.
  • VM backup operations with RCT require the Hyper-V VM configuration version 6.2 or later. If the Hyper-V VM was created on the Windows Server ≤ 2012 R2 and was later moved to a Windows Server 2016 host server (or the host server was upgraded to Windows Server 2016), you must take the VM offline and upgrade the VM configuration version before it can be backed up with RCT.
  • Make sure your Hyper-V environment is configured properly, as described in Hyper-V Configuration.

Hyperconverged Hyper-V Cluster with S2D

SEP sesam supports Hyper-Converged Infrastructure (HCI). In a Hyperconverged Hyper-V Cluster with S2D environment you can perform backup and restore of the VMs and cluster nodes. For more information see section Disaster recovery of HCI.

Configuring Hyper-V backup with RCT

The virtual machines on Hyper-V have to be backed up individually by configuring a backup task for each VM running on a Hyper-V standalone server or a Hyper-V cluster. For details, see section Creating a backup task for each VM below.

You can assign individual backup tasks to a task group and then trigger the backup of all tasks belonging to that group with a single event. The tasks are processed according to the number of available channels. The remaining tasks are placed in the execution queue and are started sequentially. For details, see Adding a Task to the Task Group.

You can also add your backup task to an existing schedule by double-clicking the backup task, selecting the tab Schedules and adding it to one or more schedules. For details, see Creating a Schedule.

Once you have configured a schedule, you must create a new backup event for it. For details, see Creating a Backup Event.

Creating a backup task for each VM

You have to create a separate task for each VM running on a Hyper-V standalone server or a Hyper-V cluster.

You can automate the process by automatically generating tasks for VMs associated to the same host. For instructions see Automatic Task Generation.

To create a backup task for a VM manually:

  1. From Main Selection -> Tasks -> By Clients, select Hyper-V client (Hyper-V standalone server or Hyper-V cluster resource) and click New Backup Task. The New Backup Task window opens.
  2. Specify the Source. Browse for the VM that you want to include in the backup and select it. Note that you can only configure one VM per backup task. By selecting the source, the task type and task name are set automatically.
  3. If you want to define other options (such as pre/post backup and restore commands, set encryption or compress data, specify OS credentials, consolidate individual tasks under a specific task group, assign a task to the schedule), click the corresponding tabs in the New Backup Task window. Click OK to create the task.

Disaster recovery of Hyper-Converged Infrastructure (HCI)

To prepare for disaster recovery of your HCI environment it is recommended to have periodic backups of the hyper-converged infrastructure. This includes backing up:

  • all essential Hyper-V VMs
  • system state of the cluster node (the node which is at the time serving the IP name).

With the system state backup, the cluster registry database is included in that backup. In case of failure of the entire cluster or a node in the cluster, the recovery can be performed using the system state backup.

To back up the virtual machines on Hyper-V, see section Configuring Hyper-V backup with RCT. For general details on configuring a backup and its prerequisites, see Standard Backup Procedure.

To prepare for disaster recovery of the Hyper-V cluster node, perform the following:

Create a system state backup task of your Hyper-V cluster node
A system state backup of the Hyper-V cluster node, performed while the Cluster Service is running, includes the cluster registry database.
Configuring a system state backup involves creating a System State backup task for your Hyper-V cluster node, setting up a backup schedule (which specifies when you want to back up your data) and linking the schedule to a backup event (which specifies how and where to back up the data). For more details refer to Backing up System State.
Test disaster recovery of HCI
It is highly recommended to perform test disaster recovery of your Hyper-V cluster or cluster node periodically. Perform restore of your Hyper-V cluster node and check functionality and integrity of the cluster.
The customer is responsible to prepare, execute and test disaster recovery plans of their HCI environment. SEP cannot guarantee successful disaster recovery of HCI environment and is not responsible in case disaster recovery fails.

Monitoring backups

You can view the status of your backup jobs in the GUI (Monitoring -> Health Check -> Last Backup State or Job State -> Backups) or SEP sesam Web UI. The backup status overview provides detailed information about the last run of backup jobs, including the task name, start and stop time of the last backup, backup level, data size, throughput, assigned media pool, etc.

See also

Hyper-V BackupAutomating Backup ProcessHyper-V RestoreHyper-V Configuration

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