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Live Recovery for Nutanix Prism Element Restores

The Live Recovery feature enables virtual machines (VMs) in a Nutanix Prism Element (AHV) environment to be recovered and powered on directly from a backup without waiting for a full restore of the VM. This feature can be used to recover a failed VM that must be returned to production quickly, or to validate that a backup can be used in a disaster recovery scenario.

Recovery Process

During Live Recovery, data is restored from the backup on demand to satisfy read requests generated by the VM. The full restore runs in the background and completes as resources allow. The backup copy is not modified during the restore process.

The process for a Live Recovery is:

  1. When this option is selected for a restore, the operation can use the MediaAgent that performed the backup. If a passkey is configured for restores, you must provide the passkey.

  2. Instead of performing a traditional full restore, the backup is exposed from the MediaAgent to the Nutanix AHV cluster as a network file system (NFS) export.

  3. The NFS export is mounted to the target Nutanix cluster and presented to the AHV hosts.

  4. The restore process retrieves the VM configuration and disk metadata required to register the VM in Prism Element.

  5. The VM configuration is updated to allow writes to the virtual disks located on the NFS-mounted datastore, or optionally to redirect writes to a specified Nutanix storage container.

  6. Once the VM files are accessible, the VM is registered in the Nutanix cluster and can be powered on from the NFS-mounted location.

  7. Read requests for the VM disks are handled by the VSA access node (MediaAgent), which restores the requested data blocks to the 3DFS cache and presents them to the AHV host.

  8. After the initial reads required to make the VM operational are completed, a background disk migration is initiated to move the virtual disks from the NFS-mounted location to the destination Nutanix storage container specified for the restore.

  9. When the migration is complete, the NFS export is unmounted and removed from the cluster (if it is no longer in use). After cleanup is finished, the restore job is marked as complete.

Considerations

  • Live VM recovery is supported for recovery from the following types of backups:

    • Streaming backups and backup copies that use magnetic disk libraries

    • IntelliSnap backups using supported vendors and engines that allow Live VM Recovery

  • Live VM recovery is not supported for the following operations:

    • Backups to tape libraries

    • Archived VMs

    • Multiple VM restores in the same job

    • Simultaneous live recovery and live browse operations for the same virtual machine

  • The operating system of the MediaAgent used for Live Recovery does not need to match the operating system of the guest VM. For example, a Windows MediaAgent can be used to recover a Linux VM running on Nutanix AHV.

  • The Live Recovery feature uses a 3DFS cache on the MediaAgent that performs the recovery. By default, the 3DFS cache is located in the Job Results folder for the MediaAgent. You can change this location using the s3dfsRootDir additional setting.

  • The 3DFS cache operates as a circular cache. Unused data is automatically pruned as needed. By default, 5% free space is maintained on the cache. You can modify this value using the n3dfsCacheMinFree additional setting.

  • For faster recovery times, host the 3DFS cache on a solid-state drive (SSD) using flash-based storage.

For each Live Recovery job, the 3DFS cache requires minimum free space equal to the larger of the following:

  • 20 GB

  • 15% of the total VM size (the sum of the sizes of all virtual disks for the VM)

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