總結，

資料表的複製 db.runCommand({cloneCollection:"commit.daxue",from:"198.61.104.31:27017"});

資料庫的複製  db.copyDatabase("user","user","198.61.104.31:27017");

對gridfs也OK哦。

http://blog.csdn.net/xiaoping8411/article/details/7691064

1、克隆collection
        1）克隆遠端colletion，使用cloneCollection命令完成將遠端的collection複製到本地。
           命令格式：db.runCommand({cloneCollection:"集合",from:"原機器",copyIndexes:false}),copyIndexes:是否複製索引
           例子：132.42.33.175上test庫t1表上有一條資料
                > db.t1.find()
                        { "_id" : ObjectId("4fd9a4bf186cb1b6ac95907d"), "name" : "liangzhangping", "addr" : "beijing" }
                132.42.33.190上test庫上t1表有兩條條資料
                > db.t1.find()
                { "_id" : ObjectId("4fd9c517dcde2d0e33d08c76"), "name" : "liangzhangping", "age" : 28 }
                { "_id" : ObjectId("4fda1795a3d56c6a40f2bc26"), "name" : "liangzhangping", "addr" : "jiangxi" }
                
                現在將132.42.33.175上test庫t1表的資料克隆到132.42.33.190上test庫上t1表上，操作如下：
                a、登入132.42.33.190機器上執行：
                        > db.runCommand({cloneCollection:"test.t1",from:"132.42.33.175:28010"})
                        { "ok" : 1 }
                b、檢視驗證