Как подключится из Node.Js к replica MongoDB?

День добрый!
Ситуация в следующем, есть три сервера реплики (отдельные машины). Как в Nodejs сделать подключение к реплики?
У меня сейчас так:

var ReplSet = require('mongodb').ReplSet
var Server = require('mongodb').Server
var Db = require('mongodb').Db
var ObjectId = require('mongodb').ObjectID

var replSet = new ReplSet([
    new Server('111.222.333.444', 27017),
    new Server('111.222.333.555', 27017),
    new Server('111.222.333.666', 27017)
  ],
  {rs_name: 'test'}, {read_secondary:true}, {w:2}, {auto_reconnect: true}
);

var db = new Db('GreatDB', replSet);

Подключается, читает и пишет в базу, но постоянно при подключении выдает следующие:

Please ensure that you set the default write concern for the database by setting    =
=   one of the options                                                                 =
=     w: (value of > -1 or the string 'majority'), where < 1 means                     =
=        no write acknowlegement                                                       =
=     journal: true/false, wait for flush to journal before acknowlegement             =
=     fsync: true/false, wait for flush to file system before acknowlegement           =
=  For backward compatibility safe is still supported and                              =
=   allows values of [true | false | {j:true} | {w:n, wtimeout:n} | {fsync:true}]      =
=   the default value is false which means the driver receives does not                =
=   return the information of the success/error of the insert/update/remove            =
=   ex: new Db(new Server('localhost', 27017), {safe:false})                           =
=   http://www.mongodb.org/display/DOCS/getLastError+Command                           =
=  The default of no acknowlegement will change in the very near future                =
=  This message will disappear when the default safe is set on the driver Db