用Percona XtraBackup的备份在slave上进行恢复的时候遇到下述错误：
Master 版本：5.6.17
Slave 版本：5.6.21-enterprise-commercial-advanced-log
mysqld_safe mysqld from pid file /data/UAT-mysql02.pid ended
mysqld_safe Starting mysqld daemon with databases from /data
2014-11-10 18:03:34 7603 [Note] Plugin 'FEDERATED' is disabled.
/bin/mysqld: Table 'mysql.plugin' doesn't exist
[ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
[Warning] InnoDB: Doublewrite does not have page_no=0 of space: 0
[ERROR] InnoDB: space header page consists of zero bytes in data file /data/ibdata1
[ERROR] InnoDB: Could not open or create the system tablespace. If you tried to add new data files to the s
ystem tablespace, and it failed here, you should now edit innodb_data_file_path in my.cnf back to what it was, and remove the new ib
data files InnoDB created in this failed attempt. InnoDB only wrote those files full of zeros, but did not yet use them in any way.
But be careful: do not remove old data files which contain your precious data!
[ERROR] Plugin 'InnoDB' init function returned error.
[ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
[ERROR] Unknown/unsupported storage engine: InnoDB
[ERROR] Aborting
网上大多数的解决办法是在运行初始化权限表的时候使用增加参数--datadir ，命令格式为：
shell> scripts/mysql_install_db --user=mysql --datadir=/usr/local/mysql/var
但这种方法并不适用。
检查my.cnf 看到 read_only= on ，注释掉，重新启动mysql，ok。
