MySQL sharding (fragmentation) Introduction _mysql

1, Sharding application scenarios are generally those?

When the amount of data in the database becomes larger and bigger, the pressure becomes larger, both read and write. Imagine, if the data in a table reached tens of millions of millions of levels, whether the index, optimize caching, etc., will face tremendous performance pressure. Sharding to reduce the pressure on a single machine by spreading the data from the same database to multiple databases or multiple machines in a certain condition.

Online games, IM, BSP are more suitable for Sharding application scenarios;

2, sharding and database partition (Partition) the difference?

Sharding realizes distributed deployment of data, the data through a series of segmentation rules, the data distributed to different DB servers, through routing rules to access the specific database, so that each visit is not a single server, but n servers, which reduces the pressure of a single server.

The partition only implements partitions within DB and cannot be deployed across servers.

The word "Shard" in English means "fragmentation", and the technical terminology used as a database appears to have been found in large multiplayer online role-playing games (MMORPG). "Sharding" is called "fragmentation".

Sharding is not a new technology, but a relatively simple concept of software. As you know, the data table partitioning feature is available after MySQL 5, so many MySQL potential users are concerned about MySQL extensibility, and partitioning is a key indicator of whether or not a database is scalable (not the only metric). Database extensibility is an eternal topic, and MySQL's promoter is often asked how to do this, such as processing application data on a single database that needs to be partitioned, and so on. The answer is: Sharding.

Sharding is not a feature of a particular database software, but an abstraction over specific technical details, a solution that extends horizontally (Scale out, or horizontally, and outwards), with the primary purpose of breaking the I/O capability limits of a single node database server, Resolves the problem of database extensibility.