InnoDB stores all records inside a fixed-size unit which is commonly called a “page”. Therefore InnoDB (XtraDB) very inefficiently uses disk space. Try to change row_format to dynamic or compressed (InnoDB compression can increase CPU load in many times).
TokuDB with lzma/lzo compression will be 2-3 times smaller than MyISAM table, and faster InnoDB .
Similar topic: [URL=“The table size between InnoDB and MyISAM engines differs in 7 times - Other MySQL® Questions - Percona Community Forum”]https://www.percona.com/forums/quest...ers-in-7-times[/URL]