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mysql innodb：innodb_flush_method

[英]mysql innodb:innodb_flush_method

原文 2010-05-04 03:47:33 3 2 mysql/ innodb

in the following link 在以下链接中

http://dev.mysql.com/doc/refman/5.1/en/innodb-parameters.html#sysvar_innodb_flush_method http://dev.mysql.com/doc/refman/5.1/en/innodb-parameters.html#sysvar_innodb_flush_method

it says:Different values of this variable can have a marked effect on InnoDB performance. 它说：这个变量的不同值可以对InnoDB性能产生显着影响。 For example, on some systems where InnoDB data and log files are located on a SAN, it has been found that setting innodb_flush_method to O_DIRECT can degrade performance of simple SELECT statements by a factor of three. 例如，在InnoDB数据和日志文件位于SAN上的某些系统上， 已发现将innodb_flush_method设置为O_DIRECT会使简单SELECT语句的性能降低三倍。

Why O_DIRECT could slow down the select statement? 为什么O_DIRECT会降低select语句的速度？

2 个解决方案

O_DIRECT bypasses the OS's cacheing systems. O_DIRECT绕过操作系统的缓存系统。 A SAN may be a very fast storage system, but generally it's going to be somewhere else over a network link and proxied/hidden behind various other layers. SAN可能是一个非常快速的存储系统，但通常它将通过网络链接在其他地方并代理/隐藏在各种其他层之后。 By using O_DIRECT, which eliminates local cacheing, you force InnoDB to hit the storage system directly every time. 通过使用消除本地缓存的O_DIRECT，您可以强制InnoDB每次都直接访问存储系统。

You really need to experiment with the flush method on your hardware to see what works best for you. 您真的需要在硬件上试验flush方法，看看哪种方法最适合您。 Setting: 设置：

innodb_flush_method = O_DIRECT innodb_flush_method = O_DIRECT

Improved our performance by 15% on a Dell 2950 server with 15K RPM SAS drives configured in RAID 1 configuration with Dell's PERC caching controller. 使用戴尔PERC缓存控制器在RAID 1配置中配置15K RPM SAS驱动器的Dell 2950服务器上，我们的性能提高了15％。 We're running Ubuntu 9.04 stock kernel and most of the work is mysql using innodb. 我们正在运行Ubuntu 9.04库存内核，大部分工作都是使用innodb的mysql。 Your mileage may vary. 你的旅费可能会改变。