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By default, when InnoDB  creates a new data file, such as a new log file or tablespace file, the file is fully written to the operating system cache before it is flushed to disk, which can cause a large amount of disk write activity to occur at once. To force smaller, periodic flushes of data from the operating system cache, you can use the innodb_fsync_threshold  variable to define a threshold value, in bytes. When the byte threshold is reached, the contents of the operating system cache are flushed to disk. The default value of 0 forces the default behavior, which is to flush data to disk only after a file is fully written to the cache. 

Specifying a threshold to force smaller, periodic flushes may be beneficial in cases where multiple MySQL instances use the same storage devices. For example, creating a new MySQL instance and its associated data files could cause large surges of disk write activity, impeding the performance of other MySQL instances that use the same storage devices. Configuring a threshold helps avoid such surges in write activity. 

• innodb_ft_aux_table 

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Specifies the qualified name of an InnoDB  table containing a FULLTEXT  index. This variable is intended for diagnostic purposes and can only be set at runtime. For example: 

SET GLOBAL innodb_ft_aux_table = ’test/t1’; 

After you set this variable to a name in the format db_name / table_name , the INFORMATION_SCHEMA tables INNODB_FT_INDEX_TABLE , INNODB_FT_INDEX_CACHE , INNODB_FT_CONFIG , INNODB_FT_DELETED , and INNODB_FT_BEING_DELETED  show information about the search index for the specified table. 

For more information, see Section 15.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables” . 

• innodb_ft_cache_size 

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