'Returns size of volume to be managed by manage_existing.'

def manage_existing_get_size(self, volume, existing_ref):

    lun = self._get_referenced_lun(existing_ref)
    target_pool = utils.get_pool_from_host(volume.host)
    if (target_pool and (lun.pool_name != target_pool)):
        reason = (_('The    imported    lun    is    in    pool    %(lun_pool)s    which    is    not    managed    by    the    host    %(host)s.') % {'lun_pool': lun.pool_name, 'host': volume['host']})
        raise exception.ManageExistingInvalidReference(existing_ref=existing_ref, reason=reason)
    return lun.total_capacity_gb
