Support availability zone in volume type

This blueprint proposes to support setting a volume type’s availability zones.

Problem description

In a newly deployed region environment, the volume type (SSD, HDD or others) may only exist on part of the AZs, but end users have no idea which AZ is allowed for one specific volume type and they can’t realize that only when the volume failed to be scheduled to backend.

Use Cases

Administrators can update the available AZs for volume type and UI or end users can know valid volume types in current AZ.

Proposed change

As the discussion result during Rocky PTG [1], we would propose to use volume type’s extra specs to support this. Since extra specs is designed for generic use, we would propose to introduce a reserved key os-extended:availability_zones for extra specs. Administrator can create/update this attribute in the format as below to support AZ in volume type:

"volume_type": {
    "id": "6685584b-1eac-4da6-b5c3-555430cf68ff",
    "name": "az_type",
    "description": "availability zone type 001",
    "is_public": true,
    "extra_specs": {
        "os-extended:availability_zones": "az1,az2,az3"

NOTE: Our capability filter will skip any extra spec which has key in the format of “prefix:key_name”. Since this use case is more related to UI or other endpoint concerns, we would also propose to support filter volume type via extra specs as well:

Request example:

Also, it’s mentionable that the extra spec availability zones will be handled in a slightly different way when compared with the rest during filtering. Cinder will always try inexact match for this specific value, for instance, when extra spec os-extended:availability_zones is set as below, both az1 and az2 are valid input for query:

"os-extended:availability_zones": "az1,az2,az3"

In order to fully support type’s AZ in Cinder, there are also some changes on Cinder framework.

  1. Now the intersection of AZs between volume type’s and other inputs (user input, source resource or default configuration) will be calculated when creating a new volume and 400 Bad Request will be raised if this intersection is empty.

  2. It’s possible now we could pass an AZ list to the scheduler when creating or retyping, workflow and AvailabilityZoneFilter will be updated to support this.

NOTE: Cinder will raise 400 Bad Request as well if type’s availability_zones attribute is set but value is empty.



Data model impact


REST API impact

  1. Now Cinder supports filter volume type with extra specs:

    GET: /V3/{tenant_id}/types?extra_specs={'spec_name':'spec_value'}
    Response BODY:
        "volume_types": [{
            "name": "volume_type1",
            "description": "volume_type1",
            "extra_specs": {"spec_name": "spec_value"},
  2. API version bump will be required for these changes.

Cinder-client impact

Volume type’s CLIs will be updated corresponding to the API change at server side.

Security impact


Notifications impact


Other end user impact


Performance Impact

There would be a slight performance impact when filtering volume types with extra specs.

Other deployer impact


Developer impact




Primary assignee:


Work Items

  • Support availability zone and extra spec filtering in volume type API.

  • Update cinder workflow to support availability zone lists.

  • Add related unit testcases.

  • Update cinderclient to support filter volume type with extra specs.




  • Add unit tests to cover this change.

Documentation Impact

  • Update the API reference.

  • Add administrator documentation to advertise the reserved key os-extended:availability_zones and explain why&when&how should this can be used.