wiki:UpgradingToXTS2

At the moment there is only one significant note regarding XTS2:

IF YOU'RE USING MYSQL, SET THE DEFAULT ENGINE TO INNODB.

XTS2 absolutely depends on ACID compliance in the database to ensure that the baskets table and the producer tables remain in sync and that the database is never in an inconsistent state. This is implemented using SQL transactions, which MyISAM does not support.