cinder/api-ref/source/v3/samples/backup-create-request.json

{
    "backup": {
        "container": null,
        "description": null,
        "name": "backup001",
        "volume_id": "64f5d2fb-d836-4063-b7e2-544d5c1ff607",
        "incremental": true,
        "availability_zone": "AZ2",
        "metadata": null
    }
}