setup mongo sharding, a sample configuration and testing sharding behavior.

Terminal 1
mongod --port 27022 --dbpath /config --configsvr

Terminal 2
mongos --configdb localhost:27022 --port 27034 --chunkSize 1

Termail 3
mongod --port 27023 --dbpath /app/mongo/shards/shard0/data --shardsvr

Termail 4
mongod --port 27024 --dbpath /app/monngo/shards/shard1/data -shardsvr

Connect to mongos
mongo localhost:27034


mongos>  db.runCommand({addshard : "localhost:27023",allowLocal: true})
{ "shardAdded" : "shard0000", "ok" : 1 }
mongos> db.runCommand({addshard : "localhost:27024",allowLocal: true})
{ "shardAdded" : "shard0001", "ok" : 1 }

mongos> testdb = db.getSisterDB("testdb");

testdb

mongos> db.runCommand({ enablesharding:"testd"})

{ "ok" : 1 }

mongos> db.runCommand({ enablesharding:"testdb"})

{ "ok" : 1 }

mongos> db.runCommand({ enablesharding:"testdb"})

{ "ok" : 0, "errmsg" : "already enabled" }

mongos> db.runCommand({shardcollection : "testdb.testcollection", key : {testkey : 1}})
{ "collectionsharded" : "testdb.testcollection", "ok" : 1 }

Use the following java to insert 200000+ rows into new db 

package dbHelper;  

import java.util.Random;

import com.mongodb.*;

import java.net.UnknownHostException;

public class InsertTester {

MongoHelper mh; 

public InsertTester (String p_hostname, int p_portnumber , String p_username, String p_password , String p_dbname) {

try {

mh = new MongoHelper(p_hostname,p_portnumber,p_username,p_password,p_dbname);

}

catch ( Exception e ) {

e.printStackTrace();

}

}

public static void main(String[] args) {

// TODO Auto-generated method stub

InsertTester tester=new InsertTester ("cvlqmongo1",27034,null,null,"testdb");

int testKey=0;

Random rd = new Random();

BasicDBObject myobj = null;

for ( int i=0; i < 10000 ; i++ ) {

testKey = rd.nextInt();

myobj=new BasicDBObject("testkey",testKey);

myobj.append("Content", "WhatEver");

   tester.mh.addContents("testcollection", myobj);

   

}

}

}

Row counts 

mongos> db.testcollection.count();

20342

Numbers in shr0 and shr1 are on pair. Almost 10000 on each node. 

Add another shard

Termial 5

mongod --port 27025 --dbpath /app/mongo/shards/shards/shard2 --shardsvr 

mogos localhost:27034

db.runCommand( { addshard : "localhost:27025", allowLocal:true});

mongos> use admin

switched to db admin

mongos> db.runCommand({listShards:1});

{

        "shards" : [

                {

                        "_id" : "shard0000",

                        "host" : "localhost:27023"

                },

                {

                        "_id" : "shard0001",

                        "host" : "localhost:27024"

                },

                {

                        "_id" : "shard0002",

                        "host" : "localhost:27025"

                }

        ],

        "ok" : 1

}

Execute testing program again.  insert 20000+ more rows. Node 3 only has 2 rows populated. 

mongos> use testdb

switched to db testdb

mongos> db.testcollection.count();

40342

Node 1: 

mongo localhost:27023

> use testdb

switched to db testdb

> db.testcollection.count();

19957

Node 2: 

 mongo localhost:27024

> use testdb

switched to db testdb

> db.testcollection.count();

20383

Node 3: 

 mongo localhost:27025

> use testdb

switched to db testdb

>  db.testcollection.count();

2