Learn and practice MySQL double-write buffer performance optimization techniques and share optimization experience

Learn and practice MySQL double-write buffering performance optimization skills and optimization experience sharing

Abstract: MySQL is one of the most widely used relational databases, and double-write buffering technology is an important feature in MySQL performance optimization techniques. This article will introduce the principle of MySQL double-write buffering, as well as how to optimize performance and share experience.

1. Introducing the principle of MySQL double-write buffering technology
   The double-write buffering technology in MySQL is proposed to solve the performance bottleneck of the InnoDB storage engine in write operations. By default, the InnoDB engine writes twice to the disk, that is, first writes the log file, and then writes the data to the data file. This method will cause each write operation to require two disk IO operations, which will have a certain impact on system performance.

In order to solve this problem, MySQL introduced double write buffering technology. When the double write buffering function is turned on, the InnoDB engine will write data to a special buffer (composed of two 1MB buffer pools). Then, the InnoDB engine will asynchronously write the data in the buffer to the double-write file on the disk. A write operation only requires one disk IO operation. This method improves write performance and reduces the number of disk IOs, thereby improving the overall performance of the system.

2. How to enable the MySQL double-write buffering function
   To enable the MySQL double-write buffering function, just add the following configuration parameters to the MySQL configuration file:

[mysqld ]
innodb_doublewrite = 1

In this way, when MySQL starts, the double write buffering function will be automatically enabled. If you need to turn off this feature, just change the value of the innodb_doublewrite parameter to 0, and then restart MySQL.

3. How to optimize MySQL double-write buffering performance
   Although double-write buffering technology can improve the writing performance of the InnoDB engine, there are still some detailed optimization points to further improve the performance of the system.

3.1 Adjust the buffer pool size
The size of the buffer pool can be adjusted by modifying the value of the innodb_doublewrite_buffers parameter. By default, it is set to 8M. If the system has sufficient memory resources, you can increase this value appropriately to provide more buffer space and thereby reduce the number of disk IOs.

3.2 Controlling the refresh frequency of the double-write buffer
The refresh frequency of the double-write buffer will also have a certain impact on system performance. You can control the refresh batch size by modifying the value of the innodb_doublewrite_batch_size parameter. Increasing this value can reduce the number of refreshes and improve performance, but it may also cause more data loss when the system crashes. Therefore, reasonable adjustments need to be made according to the conditions of the specific system.

3.3 Control the writing timing of the double-write buffer
The InnoDB engine provides two parameters (innodb_use_atomic_write and innodb_flush_neighbors), and you can control the writing timing of the double-write buffer by adjusting their values. The innodb_use_atomic_write parameter is used to control whether to use atomic writing. If set to 1, it means using atomic writing, which can reduce the number of writes to the log file. The innodb_flush_neighbors parameter is used to control the number of data file refreshes. Increasing this value can reduce the number of data file refreshes, thereby improving performance. It should be noted that modifying the values ​​of these two parameters may have a certain impact on the data consistency of the system, so adjustments need to be made carefully.

4. Optimization experience sharing

4.1 Reasonable planning of hardware resources
Double write buffering involves disk IO operations, so reasonable planning of hardware resources can improve system performance Crucial. It is recommended to use high-speed disks, such as solid-state drives (SSD), to increase disk IO speed. In addition, RAID technology can also be used to improve the concurrent processing capabilities of disk IO.

4.2 Regularly monitor system performance
By regularly monitoring the performance of the system, problems can be discovered in time and optimization strategies can be adjusted. You can use some performance monitoring tools, such as perf, pt-query-digest, etc., to collect and analyze system performance indicators.

4.3 Reasonable planning of business logic
In addition to the adjustment of hardware resources and configuration parameters, reasonable planning of business logic is also an important step to improve system performance. You can use batch inserts, batch updates, etc. to reduce the number of write operations and improve the overall performance of the system.

Summary: By learning and practicing the performance optimization skills of MySQL double-write buffering, and performing reasonable optimization according to the actual situation, the writing performance of the system can be improved. However, it should be noted that during the optimization process, the stability of the system and the consistency of the data need to be considered to avoid other problems caused by over-tuning.

Code example:

// 开启双写缓冲
SET GLOBAL innodb_doublewrite = 1;

// 调整缓冲池大小为16M
SET GLOBAL innodb_doublewrite_buffers = 16M;

// 修改双写缓冲的刷新频率为256
SET GLOBAL innodb_doublewrite_batch_size = 256;

// 使用原子写入方式
SET GLOBAL innodb_use_atomic_write = 1;

// 增大数据文件的刷新次数
SET GLOBAL innodb_flush_neighbors = 10;

The above code example is to modify the configuration parameters through the MySQL command line. In practice, the appropriate method can be selected and adjusted according to the specific situation.

References:

1. "MySQL Performance Tuning Practice"
2. "MySQL Technology Insider InnoDB Storage Engine"

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