之前xtrabackup 不能备份mariadb 10的问题，看官方文档，无意找到了答案，很简单，升级xtrabackup 到2.1.7+ 版本即可，之前用的是2.0.2版本。
官方说明：https://mariadb.com/kb/en/mariadb/mariadb-documentation/clients-and-utilities/backup-restore-and-import/backup-restore-and-import-xtrabackup/

描述如下：

If you are getting errors like this

140208 23:23:03 [Note] Found 1 prepared transaction(s) in InnoDB
140208 23:23:03 [ERROR] Found 1 prepared transactions! It means that
mysqld was not shut down properly last time and critical recovery
information (last binlog or tc.log file) was manually deleted after a
crash. You have to start mysqld with –tc-heuristic-recover switch to
commit or rollback pending transactions. 140208 23:23:03 [ERROR]
Aborting

while using XtraBackup with MariaDB 5.5 or higher, you most likely
need to upgrade XtraBackup to a 2.1.7+ version. See more details in
the bug report. Also, please note that the last comment there of
2014-01-06 about multiple XA engines can be easily misunderstood. The
problem can appear even if you are not using any other XA-capable
engines.

看官方文档的重要性呀。。。