# OpenNebula

Storware Backup & Recovery supports backup for OpenNebula in Disk Attachment Strategy with changed block tracking

* supports KVM hypervisors
* supports incremental backup
* proxy VM is required - used for the disk attachment process

![](/files/lHPB8Ajo3r8QsBYa54qV)

## Backup Strategies

### Disk Attachment CBT strategy

#### Backup process

* Both full and incremental backup is supported.
* OpenNebula SDK is used for all operations on hypervisor manager using XML-RPC API.
* Crash consistent snapshots are taken of every non excluded disk.
* For every exported disk, Storware Backup & Recovery fetch its snapshot and create a new image from it. Later, the new disk is attached to proxy VM from newly created image. After copying data from disk to new backup file, disk is detached and image removed.
* While exporting disks Storware Backup & Recovery is scanning for changes based on checksums. This allows us to later perform incremental backup using these checksums and we don’t require last snapshot to be present on OpenNebula.
* VM metadata is retrieved using API and saved to the backup file.
* Used images metadata is retrieved using API and saved to the separate backup files.

{% hint style="info" %}
Our recommendation is also to configure LVM filters on Proxy VM. You need to add all OS disks and partitions, please follow these steps: [LVM setup on Storware Backup & Recovery Node for disk attachment backup mode](/backup-and-recovery-71/deployment/common-tasks/lvm-setup-on-storware-backup-and-recovery-node-for-disk-attachment-backup-mode.md)
{% endhint %}

#### Restore process

* When restoring VM, Storware Backup & Recovery restore disks first and then create from saved metadata new VM, assigning already restored disks to this VM.
* When restoring disks that were excluded from backup, Storware Backup & Recovery create a new empty image.
* When restoring non excluded disks, Storware Backup & Recovery create a new empty image, then attach new disk to proxy VM from this image. After copying data from the backup file to the attached disk, a new image is created from the data populated disk. This disk is later detached, and the empty image is removed.
* In order to create a restored VM on OpenNebula, Storware Backup & Recovery first create a template of it, and then instantiate it. After the new VM is created, the template is removed.
* VM is always restored already in RUNNING state.
* When restoring VM we can choose SYSTEM datastore in which VM will start running after restore.
* When restoring VM we can choose IMAGE datastore in which images for VM will be created.

#### Snapshots

* Snapshot management is supported.
* OpenNebula does not allow reverting snapshot when VM is still running. Because of that, for the duration of reverting all disk snapshots, VM is suspended.
* Creating and reverting snapshots for every disk is not performed in parallel, because OpenNebula does not allow it.

## Limitations

* Currently only KVM hosts are supported.
* Export of volatile disks (VM disks that were not created from image and hold their content for the duration of VM’s deployment) is not supported.


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