Add standard for volume backup functionality

Standards/scs-XXXX-v1-volume-backup-service.md

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+---
+title: Volume Backup Functionality
+type: Standard
+status: Proposal
+track: IaaS
+---
+
+## Introduction
+
+OpenStack offers a variety of resources where users are able to transfer and store data in the infrastructure.
+A prime example of these resources are volumes which are attached to virtual machines as virtual block storage devices.
+As such they carry potentially large amounts of user data which is constantly changing at runtime.
+It is important for users to have the ability to create backups of this data in a reliable and effifcient manner.
+
+## Motivation
+
+The [volume backup functionality of OpenStack](https://docs.openstack.org/cinder/latest/admin/volume-backups.html) is a feature that is not available in all OpenStack clouds per default.
+The feature requires a backend to prepared and configured correctly before it can be used.
+In Cinder this is a separate configuration to the general storage backend of the volume service and is not mandatory.
+Thus, an arbitrary OpenStack cloud may or may not offer this feature.
+
+This standard aims to make this functionality the default in SCS clouds so that customers can expect the feature to be usable.
+
+## Design Considerations
+
+The standard should make sure that the feature is available and usable but should not limit the exact implementation (e.g. choice of backend driver) any further than necessary.
+
+### Options considered
+
+#### Only recommend volume backup feature, use images as alternative
+
+As an alternative to the volume backup feature of the Block Storage API, Glance images can also be created based on volumes and act as a backup under certain circumstances.
+As an option, this standard could keep the actual integration of the volume backup feature optional and guide users how to use images as backup targets instead in case the feature is unavailable.
+
+However, it is not guaranteed that the Glance backend storage is separate from the volume storage.
+For instance, both could be using the same Ceph cluster.
+In such case, the images would not count as genuine backups.
+
+Although users are able to download images and transfer them to a different storage location, this approach might also prove unfeasible depending on the image size and the existence (or lack) of appropriate target storage on the user side.
+
+Furthermore, incremental backups are not possible when creating Glance images from volumes either.
+This results in time-consuming backup operations of fully copying a volume everytime a backup is created.
+
+#### Mandate the availability of the volume backup feature
+
+This option is pretty straightforward.
+It would make the volume backup feature mandatory for SCS clouds.
+This way users can expect the feature to be available and usable.
+
+With this, users can leverage functionalities like incremental backups and benefit from optimized performance of the backup process due to the tight integration with the volume service.
+
+## Decision
+
+This standard decides to go with the second option and makes the volume backup feature mandatory in the following way:
+
+In an SCS cloud, the volume backup functionality MUST be configured properly and its API as defined per `/v3/{project_id}/backups` MUST be offered to customers.
+If using Cinder, a suitable [backup driver](https://docs.openstack.org/cinder/latest/configuration/block-storage/backup-drivers.html) MUST be set up.
+
+The volume backup target storage SHOULD be a separate storage system from the one used for volumes themselves.
+
+## Related Documents
+
+- [OpenStack Block Storage v3 Backup API reference](https://docs.openstack.org/api-ref/block-storage/v3/index.html#backups-backups)
+
+## Conformance Tests
+
+Conformance tests include using the `/v3/{project_id}/backups` Block Storage API endpoint to create a volume and a backup of it as a non-admin user and subsequently restore the backup on a new volume while verifying the success of each operation.
+
+There is a test suite in [`volume-backup-tester.py`](https://github.com/SovereignCloudStack/standards/blob/main/Tests/iaas/volume-backup/volume-backup-tester.py).
+The test suite connects to the OpenStack API and executes basic operations using the volume backup API to verify that the functionality requested by the standard is available.
+Please consult the associated [README.md](https://github.com/SovereignCloudStack/standards/blob/main/Tests/iaas/volume-backup/README.md) for detailed setup and testing instructions.

Tests/iaas/volume-backup/README.md

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+# Volume Backup API Test Suite
+
+## Test Environment Setup
+
+### Test Execution Environment
+
+> **NOTE:** The test execution procedure does not require cloud admin rights.
+
+To execute the test suite a valid cloud configuration for the OpenStack SDK in the shape of "`clouds.yaml`" is mandatory[^1].
+**The file is expected to be located in the current working directory where the test script is executed unless configured otherwise.**
+
+[^1]: [OpenStack Documentation: Configuring OpenStack SDK Applications](https://docs.openstack.org/openstacksdk/latest/user/config/configuration.html)
+
+The test execution environment can be located on any system outside of the cloud infrastructure that has OpenStack API access.
+Make sure that the API access is configured properly in "`clouds.yaml`".
+
+It is recommended to use a Python virtual environment[^2].
+Next, install the OpenStack SDK required by the test suite:
+
+```bash
+pip3 install openstacksdk
+```
+
+Within this environment execute the test suite.
+
+[^2]: [Python 3 Documentation: Virtual Environments and Packages](https://docs.python.org/3/tutorial/venv.html)
+
+## Test Execution
+
+The test suite is executed as follows:
+
+```bash
+python3 volume-backup-tester.py --os-cloud mycloud
+```
+
+As an alternative to "`--os-cloud`", the "`OS_CLOUD`" environment variable may be specified instead.
+The parameter is used to look up the correct cloud configuration in "`clouds.yaml`".
+For the example command above, this file should contain a `clouds.mycloud` section like this:
+
+```yaml
+---
+clouds:
+  mycloud:
+    auth:
+      auth_url: ...
+      ...
+    ...
+```
+
+If the test suite fails and leaves test resources behind, the "`--cleanup-only`" flag may be used to delete those resources from the domains:
+
+```bash
+python3 volume-backup-tester.py --os-cloud mycloud --cleanup-only
+```
+
+For any further options consult the output of "`python3 volume-backup-tester.py --help`".
+
+### Script Behavior & Test Results
+
+> **NOTE:** Before any execution of test batches, the script will automatically perform a cleanup of volumes and volume backups matching a special prefix (see the "`--prefix`" flag).
+> This cleanup behavior is identical to "`--cleanup-only`".
+
+The script will print all cleanup actions and passed tests to `stdout`.
+
+If all tests pass, the script will return with an exit code of `0`.
+
+If any test fails, the script will halt, print the exact error to `stderr` and return with a non-zero exit code.
+
+In case of a failed test, cleanup is not performed automatically, allowing for manual inspection of the cloud state for debugging purposes.
+Although unnecessary due to automatic cleanup upon next execution, you can manually trigger a cleanup using the "`--cleanup-only`" flag of this script.