As of MySQL 5.5, the default storage engine should change from MyISAM to InnoDB.
InnoDB should be the default storage engine for all user created objects in the regular and enterprise versions of MySQL. MyISAM will remain the default engine for the embedded server. System tables will still remain in MyISAM tables InnoDB code should be mandatory in the build (except for the embedded server), so it should not be possible to exclude InnoDB support when building MySQL server. Upgrade/downgrade scenarios should not be affected by this change. If a table is MyISAM before upgrade/downgrade, it should continue to be so. The regression test suite will need to be examined and changed to ensure that MyISAM related regression tests have an explicit "engine=MyISAM" clause. Since MyISAM so far has been the default, some of these test cases may have omitted the engine clause. Change the following default values: (as per recommendations from the InnoDB team) innodb_file_format -> Barracuda (was: Antelope) innodb_strict_mode -> TRUE (was: FALSE) innodb_file_per_table -> TRUE (was: FALSE) Note: the changes to the default values were reverted back in 5.5 due to replication failures.