InnoDB tables are stored in storage areas called
tablespaces, which contain both data and indexes. In older MariaDB versions, by default, InnoDB used only one tablespace called the system tablespace. It also contains the change buffer, the doublewrite buffer, and by default, the undo log. This tablespace is physically stored in the
ibdata file in the
data directory of MariaDB (
ibdata2, and so on). While the system tablespace still exists on the latest versions of MariaDB and can still contain all the tables, it is now possible to store each new table in a dedicated tablespace. Each tablespace created in this way is a separate file with the
.ibd extension, which is located in a database subdirectory. ...