Create block storage device

def volume_create(name, size=100, snapshot=None, voltype=None, **kwargs):
    '''
    Create block storage device
    '''
    conn = get_conn()
    create_kwargs = {'name': name,
                     'size': size,
                     'snapshot': snapshot,
                     'voltype': voltype}
    create_kwargs['availability_zone'] = kwargs.get('availability_zone', None)
    return conn.volume_create(**create_kwargs)