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# MongoDB Sharding * * * ## Sharding In MongoDB, there is another type of cluster called sharding, which can meet the needs of massive data growth in MongoDB. When MongoDB stores massive amounts of data, a single machine may not be sufficient to store the data, nor may it provide acceptable read/write throughput. In such cases, we can split the data across multiple machines, enabling the database system to store and process more data. * * * ## Why Use Sharding * Replicates all write operations to the primary node * Latency-sensitive data is queried on the primary node * A single replica set is limited to 12 nodes * Memory exhaustion can occur when request volume is huge. * Local disk space is insufficient * Vertical scaling is expensive * * * ## MongoDB Sharding The diagram below illustrates the structure of a sharded cluster in MongoDB: !(#) The diagram above contains the following three main components: * **Shard:** Used to store the actual data chunks. In a production environment, a shard server role can be assumed by a replica set composed of several machines to prevent single points of failure. * **Config Server:** A mongod instance that stores the entire ClusterMetadata, including chunk information. * **Query Routers:** The front-end router through which clients connect, making the entire cluster appear as a single database. Front-end applications can use it transparently. * * * ## Sharding Example The port distribution for the sharding structure is as follows: Shard Server 1: 27020 Shard Server 2: 27021 Shard Server 3: 27022 Shard Server 4: 27023 Config Server: 27100 Route Process: 40000 Step 1: Start the Shard Servers [root@100 /]# mkdir -p /www/mongoDB/shard/s0 [root@100 /]# mkdir -p /www/mongoDB/shard/s1 [root@100 /]# mkdir -p /www/mongoDB/shard/s2 [root@100 /]# mkdir -p /www/mongoDB/shard/s3 [root@100 /]# mkdir -p /www/mongoDB/shard/log [root@100 /]# /usr/local/mongoDB/bin/mongod --port 27020 --dbpath=/www/mongoDB/shard/s0 --logpath=/www/mongoDB/shard/log/s0.log --logappend --fork .... [root@100 /]# /usr/local/mongoDB/bin/mongod --port 27023 --dbpath=/www/mongoDB/shard/s3 --logpath=/www/mongoDB/shard/log/s3.log --logappend --fork Step 2: Start the Config Server [root@100 /]# mkdir -p /www/mongoDB/shard/config [root@100 /]# /usr/local/mongoDB/bin/mongod --port 27100 --dbpath=/www/mongoDB/shard/config --logpath=/www/mongoDB/shard/log/config.log --logappend --fork **Note:** Here, we can start it just like starting a regular MongoDB service, without adding the --shardsvr and configsvr parameters. Because the function of these two parameters is to change the startup port, we can specify the port ourselves. Step 3: Start the Route Process /usr/local/mongoDB/bin/mongos --port 40000 --configdb localhost:27100 --fork --logpath=/www/mongoDB/shard/log/route.log --chunkSize 500 In the mongos startup parameters, the chunkSize item is used to specify the size of the chunk, in MB, with a default size of 200MB. Step 4: Configure Sharding Next, we use the MongoDB Shell to log in to mongos and add Shard nodes. [root@100 shard]# /usr/local/mongoDB/bin/mongo admin --port 40000 MongoDB shell version: 2.0.7 connecting to: 127.0.0.1:40000/admin mongos> db.runCommand({ addshard:"localhost:27020" }) { "shardAdded" : "shard0000", "ok" : 1 } ...... mongos> db.runCommand({ addshard:"localhost:27029" }) { "shardAdded" : "shard0009", "ok" : 1 } mongos> db.runCommand({ enablesharding:"test" }) #Set the database for sharded storage { "ok" : 1 } mongos> db.runCommand({ shardcollection: "test.log", key: { id:1,time:1}}) { "collectionsharded" : "test.log", "ok" : 1 } Step 5: No major changes are needed in the program code. Simply connect to the interface port 40000 just as you would connect to a regular MongoDB database. [](#)[MongoDB Replication (Replica Set)](#)") [MongoDB Backup (mongodump) & Restore (mongorestore)](#) & Restore (mongorestore)")[](#) [Volcengine Coding Plan supports Doubao, GLM, DeepSeek, Kimi, MiniMax and other mainstream large models, officially supplied, stable and reliable. Configuration Guide ¥9.9/month Subscribe Now](https://maas.xfyun.cn/modelSquare?ch=maas_lm_l2E) ## 1 Note Write Note 1. #0 chad li1***6@163.com (https://segmentfault.com/a/1190000012148843) [](#)139 **1. Create Sharding Replica Set rs0** # mkdir /data/log # mkdir /data/db1 # nohup mongod --port 27020 --dbpath=/data/db1 --logpath=/data/log/rs0-1.log --logappend --fork --shardsvr --replSet=rs0 & # mkdir /data/db2 # nohup mongod --port 27021 --dbpath=/data/db2 --logpath=/data/log/rs0-2.log --logappend --fork --shardsvr --replSet=rs0 & 1.1 Replica Set rs0 Configuration # mongo localhost:27020 > rs.initiate({_id: 'rs0', members: [{_id: 0, host: 'localhost:27020'}, {_id: 1, host: 'localhost:27021'}]}) > rs.isMaster() #Check primary-secondary relationship **2. Create Sharding Replica Set rs1** # mkdir /data/db3 # nohup mongod --port 27030 --dbpath=/data/db3 --logpath=/data/log/rs1-1.log --logappend --fork --shardsvr --replSet=rs1 & # mkdir /data/db4 # nohup mongod --port 27031 --dbpath=/data/db4 --logpath=/data/log/rs1-2.log --logappend --fork --shardsvr --replSet=rs1 & 2.1 Replica Set rs1 Configuration # mongo localhost:27030 > rs.initiate({_id: 'rs1', members: [{_id: 0, host: 'localhost:27030'}, {_id: 1, host: 'localhost:27031'}]}) > rs.isMaster() #Check primary-secondary relationship **3. Create Config Replica Set conf** # mkdir /data/conf1 # nohup mongod --port 27100 --dbpath=/data/conf1 --logpath=/data/log/conf-1.log --logappend --fork --configsvr --replSet=conf & # mkdir /data/conf2 # nohup mongod --port 27101 --dbpath=/data/conf2 --logpath=/data/log/conf-2.log --logappend --fork --configsvr --replSet=conf & 3.1 Replica Set conf Configuration # mongo localhost:27100 > rs.initiate({_id: 'conf', members: [{_id: 0, host: 'localhost:27100'}, {_id: 1, host: 'localhost:27101'}]}) >