Cinder Library is a Python library that allows using storage drivers provided by Cinder outside of OpenStack and without needing to run the Cinder service, so we don’t need Keystone, MySQL, or RabbitMQ services to control our storage.
The library is currently in an early development stage and can be considered as a proof of concept and not a finished product at this moment, so please carefully go over the limitations section to avoid surprises.
Due to the limited access to Cinder backends and time constraints the list of drivers that have been manually tested, and using the existing limited functional tests, are:
- LVM with LIO
- Dell EMC XtremIO
- Dell EMC VMAX
- Kaminario K2
- NetApp SolidFire
- Use a Cinder driver without running a DBMS, Message broker, or Cinder services.
- Using multiple simultaneous drivers on the same program.
- Stateless: Support full serialization of objects and context to JSON or string so the state can be restored.
- Metadata persistence plugin mechanism.
- Basic operations support:
- Create volume
- Delete volume
- Extend volume
- Clone volume
- Create snapshot
- Delete snapshot
- Create volume from snapshot
- Connect volume
- Disconnect volume
- Local attach
- Local detach
- Validate connector
Being in its early development stages the library is in no way close to the robustness or feature richness that the Cinder project provides. Some of the more noticeable limitations one should be aware of are:
- Most methods don’t perform argument validation so it’s a classic GIGO library.
- The logic has been kept to a minimum and higher functioning logic is expected to be handled by the caller.
- There is no CI, or unit tests for that matter, and certainly nothing so fancy as third party vendor CIs, so things could be broken at any point. We only have some automated, yet limited, functional tests.
- Only a subset of Cinder available operations are supported by the library.
- The only Cinder release that has been tested with the library has been Pike.
- Access to a small number of storage arrays has limited the number of drivers that have been verified to work with cinderlib.
Besides cinderlib’s own limitations the library also inherits some from Cinder’s code and will be bound by the same restrictions and behaviors of the drivers as if they were running under the standard Cinder services. The most notorious ones are:
- Dependency on the eventlet library.
- Behavior inconsistency on some operations across drivers. For example you can find drivers where cloning is a cheap operation performed by the storage array whereas other will actually create a new volume, attach the source and new volume and perform a full copy of the data.
- External dependencies must be handled manually. So we’ll have to take care of any library, package, or CLI tool that is required by the driver.
- Relies on command execution via sudo for attach/detach operations as well as some CLI tools.