Why does MariaDB 10.2 use InnoDB instead of XtraDB?，mariadbinnodb
Up until 10.1, MariaDB used Percona XtraDB as the default 'InnoDB' storage engine. From 10.2, InnoDB is the default. Why was this change made?
直到10.1版本mariadb还在使用percona的xtradb作为默认的存储引擎。10.2版本开始不再使用了，而转使用innodb，为什么？
Answer Answered by iangilfillan in this comment.
Keeping InnoDB (or XtraDB) up to date with MySQL (Percona) is a complex task. It took us more than half a year to migrate from InnoDB-5.6 to InnoDB-5.7 in 10.2. Doing it again for XtraDB would probably have required only slightly less than this. For us to embark on such project, it must bring significant benefits to our users.
使innodb或者xtradb和MySQL（perocna）保持一致是一个非常复杂的任务。从innodb5.6升级到innodb5.7将花费了将近大半年的时间。而升级xtradb的话，就不会有这么大的工作量。只有对我们用户带来重大好处时才会做这样的改动计划。
XtraDB had many great improvements over InnoDB in 5.1 and 5.5. But over time, MySQL has implemented almost all of them. InnoDB has caught up and XtraDB is only marginally better. Not enough to justify a multi-month merge that would delay 10.2-GA for everyone.
在innodb5.1到5.5，xtradb有很大的优势。但是现在MySQL已经将innodb的功能完善到和xtradb差不多了。升级innodb也不会延迟10.2-GA版本的发布。
In particular, the only real improvement that XtraDB 5.7 seems to have is for a write-intensive I/O-bound workload, where innodb_thread_concurrency control is disabled.
实际上xtradb5.7优势，仅仅只有在写敏感的IO负载下，性能有所提高。
With a proper innodb_thread_concurrency, XtraDB is only marginally better. We didn't want to delay 10.2-GA by up to half a year for the sake of those few users who have write-intensive I/O-bound InnoDB workload and don't know how to configure innodb_thread_concurrency.
innodb_thread_concurrency值适当时，xtradb的性能提高不大。这不值得我们去做。
Note, we still consider incorporating XtraDB optimizations, but as patches, rather than XtraDB as a whole, which no longer has numerous all-over-the-code improvements.
注意：我们还会持续结合xtradb优化，但只是作为分支，不会作为整个基线了。