InnoDB System Variables argument value when  InnoDB  builds a list of directories to scan at startup. These directories are appended regardless of whether an  innodb_directories  setting is specified explicitly. innodb_directories  may be specified as an option in a startup command or in a MySQL option file. Quotes surround the argument value because otherwise some command interpreters interpret semicolon ( ; ) as a special character. (For example, Unix shells treat it as a command terminator.) Startup command: mysqld --innodb-directories=" directory_path_1 ; directory_path_2 " MySQL option file: [mysqld] innodb_directories=" directory_path_1 ; directory_path_2 " Wildcard expressions cannot be used to specify directories. The  innodb_directories  scan also traverses the subdirectories of specified directories. Duplicate directories and subdirectories are discarded from the list of directories to be scanned. For more information, see Section 15.6.3.6, “Moving Tablespace Files While the Server is Offline” . Disables the operating system file system cache for merge-sort temporary files. The effect is to open such files with the equivalent of  O_DIRECT . The  innodb_doublewrite  variable controls whether the doublwrite buffer is enabled. It is enabled by default in most cases. To disable the doublewrite buffer, set  innodb_doublewrite  to 0 or start the server with  --skip-innodb-doublewrite . You might consider disabling the doublewrite buffer if you are more concerned with performance than data integrity, as may be the case when performing benchmarks, for example. 3238 • innodb_doublewrite • innodb_disable_sort_file_cache Command-Line Format --innodb-disable-sort-file- cache[={OFF|ON}] System Variable innodb_disable_sort_file_cache Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Boolean Default Value OFF Command-Line Format --innodb-doublewrite[={OFF|ON}] System Variable innodb_doublewrite Scope Global Dynamic No SET_VAR  Hint Applies No Type Boolean Default Value ON