MongoDB: The Definitive Guide

Chapter 10. Sharding

Sharding is MongoDB’s approach to scaling out. Sharding allows you to add more machines to handle increasing load and data size without affecting your application.

Introduction to Sharding

Sharding refers to the process of splitting data up and storing different portions of the data on different machines; the term partitioning is also sometimes used to describe this concept. By splitting data up across machines, it becomes possible to store more data and handle more load without requiring large or powerful machines.

Manual sharding can be done with almost any database software. It is when an application maintains connections to several different database servers, each of which are completely independent. The application code manages storing different data on different servers and querying against the appropriate server to get data back. This approach can work well but becomes difficult to maintain when adding or removing nodes from the cluster or in the face of changing data distributions or load patterns.

MongoDB supports autosharding, which eliminates some of the administrative headaches of manual sharding. The cluster handles splitting up data and rebalancing automatically. Throughout the rest of this book (and most MongoDB documentation in general), the terms sharding and autosharding are used interchangeably, but it’s important to note the difference between that and manual sharding in an application.

Autosharding in MongoDB

The basic concept behind MongoDB’s ...