While exploring some MySQL/MariaDB configurations i encountered the O_DIRECT option related to the innodb_flush_method directive.
https://dev.mysql.com/doc/refman/8.0/en/optimizing-innodb-diskio.html
https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_flush_method
So my question was. Is O_DIRECT really effective?
In short, your answer is maybe No… unless you have Solaris, but maybe it’s untrue even there.
I’ve found a very interesting lecture about this topic. This is my favorite extract:
In conclusion I can say that Linus Torvalds is once again corrent: O_DIRECT is completely useless and shouldn’t be used.
― svetlinmladenov on O_DIRECT
So, thank you Oracle! I wasted so much time because of your phrase in this stupid presentation:
InnoDB can use direct IO on systems that support it -Linux, FreeBSD, and Solaris–innodb_flush_method= O_DIRECT
― Oracle Presentation, page 15
O_DIRECT = No thanks.