Drupal 8 no longer supports MyISAM as the default storage engine

Drupal 8 no longer supports MyISAM as the default engine for MySQL, because Drupal 8 relies on transaction support, and MyISAM is non-transactional. Drupal 8 will use the InnoDB engine by default for MySQL installations (as Drupal 7 does). Only the InnoDB engine is tested and considered fully supported.

Sites using MyISAM in Drupal 7 or earlier should migrate their data to InnoDB in Drupal 8 with the Migrate module.

Note that some specific subsystems may have table needs that are lower than that of Drupal as a whole and so may be configured with alternate engines. For instance, the semaphore table (part of the locking system) can use the MEMORY engine type as long-term persistence and transactions are not needed. Such advanced configurations are the responsibility of the site developer to ensure are stable.