So, a customer reached out to us today concerning ways to use HEAT to build CBS

  blk_server:
    type: "Rackspace::Cloud::Server"
    properties:
      flavor: 15 GB Memory v1
      image: { get_param: image }
      name: "blk"
      user_data:
...

The problem is using this format they get an error

ERROR: Image Ubuntu 14.04 LTS (Trusty Tahr) (PVHVM) requires 20 GB minimum disk space. Flavor 15 GB Memory v1 has only 0 GB.

This is happening because memory flavor doesn’t use the hypervisor instance store, and instead is using Cloud Block Storage, hence ‘0GB’.
Thanks to my friend Aaron I have dug out the documentation for building CBS boot from volume server flavors. Here is how it would be done.

parameters:
  nodesize:
    type: number
    label: Nodes Disk Size
    description: Size of the each Nodes primary disk.
    default: 50
    constraints:
      - range: { min: 50, max: 1024 }
        description: must be between 50 and 1024 Gb.

    nodeimage:
    label: Operating system
    description: |
      Server image. Defaults to 'CentOS 6 (PVHVM)'.
    type: string
    default: CentOS 7 (PVHVM)
    constraints:
    - allowed_values:
      - CentOS 7 (PVHVM)
      - Red Hat Enterprise Linux 7 (PVHVM)
      description: Must be a supported operating system.

  
  elk_server:
    type: "Rackspace::Cloud::Server"
    properties:
      flavor: 15 GB Memory v1
      block_device_mapping: [{ device_name: "vda", volume_id : { get_resource : cinder_volume }, delete_on_termination : "true" }]
      name: "elk"
      user_data:
  
    cinder_volume:
    type: OS::Cinder::Volume
    properties:
      size: { get_param: nodesize }
      image: { get_param: nodeimage }