I have convert some tables in database from MyISAM to InnoDB. After that, I see some modification on file system.
The size of database is grown up, from 2.8GB to 4.8GB and there are many file with prefix FTS_* like
FTS_000000000000005c_00000000000000f3_INDEX_1.ibd FTS_000000000000005c_00000000000000f3_INDEX_2.ibd FTS_000000000000005c_00000000000000f3_INDEX_3.ibd FTS_000000000000005c_00000000000000f3_INDEX_4.ibd FTS_000000000000005c_00000000000000f3_INDEX_5.ibd FTS_000000000000005c_00000000000000f3_INDEX_6.ibd FTS_000000000000005c_BEING_DELETED_CACHE.ibd FTS_000000000000005c_BEING_DELETED.ibd FTS_000000000000005c_CONFIG.ibd FTS_000000000000005c_DELETED_CACHE.ibd FTS_000000000000005c_DELETED.ibd FTS_0000000000000075_0000000000000118_INDEX_1.ibd FTS_0000000000000075_0000000000000118_INDEX_2.ibd FTS_0000000000000075_0000000000000118_INDEX_3.ibd FTS_0000000000000075_0000000000000118_INDEX_4.ibd FTS_0000000000000075_0000000000000118_INDEX_5.ibd FTS_0000000000000075_0000000000000118_INDEX_6.ibd FTS_0000000000000075_BEING_DELETED_CACHE.ibd FTS_0000000000000075_BEING_DELETED.ibd FTS_0000000000000075_CONFIG.ibd FTS_0000000000000075_DELETED_CACHE.ibd FTS_0000000000000075_DELETED.ibd
I am using MariaDB and turning innodb_file_per_table on.