原理看懂了，但是对于add/remove node的时候要怎么做还是不清楚。怎么样在add
node以后怎么样找到需要move的item?
还有比如：
what’s the best way to cope with servers of different sizes;
how to add and remove more than one machine at a time;
how to cope with replication and fault-tolerance;
没啥思路求大牛指点
