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manila/doc/source/contributor/driver_requirements.rst

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Manila minimum requirements and features since Mitaka

In order for a driver to be accepted into manila code base, there are certain minimum requirements and features that must be met, in order to ensure interoperability and standardized manila functionality among cloud providers.

At least one driver mode (DHSS true/false)

Driver modes determine if the driver is managing network resources (DHSS = true) in an automated way, in order to segregate tenants and private networks by making use of manila Share Networks, or if it is up to the administrator to manually configure all networks (DHSS = false) and be responsible for segregation, if that is desired. At least one driver mode must be supported. In DHSS = true mode, Share Server entities are used, so the driver must implement functions that setup and teardown such servers.

At least one file system sharing protocol

In order to serve shares as a shared file system service, the driver must support at least one file system sharing protocol, which can be a new protocol or one of the currently supported protocols. The current list of supported protocols is as follows:

  • NFS
  • CIFS
  • GlusterFS
  • HDFS
  • MapRFS
  • CephFS

Access rules

Access rules control how shares are accessible, by whom, and what the level of access is. Access rule operations include allowing access and denying access to a given share. The authentication type should be based on IP, User and/or Certificate. Drivers must support read-write and read-only access levels for each supported protocol, either through individual access rules or separate export locations.

Shares

Share servicing is the core functionality of a shared file system service, so a driver must be able to create and delete shares.

Share extending

In order to best satisfy cloud service requirements, shares must be elastic, so drivers must implement a share extend function that allows shares' size to be increased.

Capabilities

In order for manila to function accordingly to the driver being used, the driver must provide a set of information to manila, known as capabilities, as follows:

  • share_backend_name: a name for the backend;
  • driver_handles_share_servers: driver mode, whether this driver instance handles share servers, possible values are true or false;
  • vendor_name: driver vendor name;
  • driver_version: current driver instance version;
  • storage_protocol: list of shared file system protocols supported by this driver instance;
  • total_capacity_gb: total amount of storage space provided, in GB;
  • free_capacity_gb: amount of storage space available for use, in GB;
  • reserved_percentage: percentage of total storage space to be kept from being used.

Certain features, if supported by drivers, need to be reported in order to function correctly in manila, such as:

  • dedupe: whether the backend supports deduplication;
  • compression: whether the backend supports compressed shares;
  • thin_provisioning: whether the backend is overprovisioning shares;
  • pools: list of storage pools managed by this driver instance;
  • qos: whether the backend supports quality of service for shares;
  • replication_domain: string specifying a common group name for all backends that can replicate between each other;
  • replication_type: string specifying the type of replication supported by the driver. Can be one of ('readable', 'writable' or 'dr').

Continuous Integration systems

Every driver vendor must supply a CI system that tests its drivers continuously for each patch submitted to OpenStack gerrit. This allows for better QA and quicker response and notification for driver vendors when a patch submitted affects an existing driver. The CI system must run all applicable tempest tests, test all patches Jenkins has posted +1 and post its test results.

Unit tests

All drivers submitted must be contemplated with unit tests covering at least 90% of the code, preferably 100% if possible. Unit tests must use mock framework and be located in-tree using a structure that mirrors the functional code, such as directory names and filenames. See template below:

manila/[tests/]path/to/brand/new/[test_]driver.py

Documentation

Drivers submitted must provide and maintain related documentation on openstack-manuals, containing instructions on how to properly install and configure. The intended audience for this manual is cloud operators and administrators. Also, driver maintainers must update the manila share features support mapping documentation found at https://docs.openstack.org/manila/latest/contributor/share_back_ends_feature_support_mapping.html

Manila optional requirements and features since Mitaka

Additional to the minimum required features supported by manila, other optional features can be supported by drivers as they are already supported in manila and can be accessed through the API.

Snapshots

Share Snapshots allow for data respective to a particular point in time to be saved in order to be used later. In manila API, share snapshots taken can only be restored by creating new shares from them, thus the original share remains unaffected. If Snapshots are supported by drivers, they must be crash-consistent.

Managing/Unmanaging shares

If DHSS = false mode is used, then drivers may implement a function that supports reading existing shares in the backend that were not created by manila. After the previously existing share is registered in manila, it is completely controlled by manila and should not be handled externally anymore. Additionally, a function that de-registers such shares from manila but do not delete from backend may also be supported.

Share shrinking

Manila API supports share shrinking, thus a share can be shrunk in a similar way it can be extended, but the driver is responsible for making sure no data is compromised.

Share ensuring

In some situations, such as when the driver is restarted, manila attempts to perform maintenance on created shares, on the purpose of ensuring previously created shares are available and being serviced correctly. The driver can implement this function by checking shares' status and performing maintenance operations if needed, such as re-exporting.

Manila experimental features since Mitaka

Some features are initially released as experimental and can be accessed by including specific additional HTTP Request headers. Those features are not recommended for production cloud environments while in experimental stage.

Share Migration

Shares can be migrated between different backends and pools. Manila implements migration using an approach that works for any manufacturer, but driver vendors can implement a better optimized migration function for when migration involves backends or pools related to the same vendor.

Share Groups (since Ocata)

The share groups provides the ability to manage a group of shares together. This feature is implemented at the manager level, every driver gets this feature by default. If a driver wants to override the default behavior to support additional functionalities such as consistent group snapshot, the driver vendors may report this capability as a group capability, such as: Ordered writes, Consistent snapshots, Group replication.

Note

for more information please see group capabilities

Share Replication

Replicas of shares can be created for either data protection (for disaster recovery) or for load sharing. In order to utilize this feature, drivers must report the replication_type they support as a capability and implement necessary methods.

More details can be found at: https://docs.openstack.org/manila/latest/contributor/share_replication.html

Update "used_size" of shares

Drivers can update, for all the shares created on a particular backend, the consumed space in GiB. While the polling interval for drivers to update this information is configurable, drivers can choose to submit cached information as necessary, but specify a time at which this information was "gathered_at".