简介
innodb_data_file_path用来指定innodb tablespace文件，如果我们不在My.cnf文件中指定innodb_data_home_dir和innodb_data_file_path那么默认会在datadir目录下创建ibdata1 作为innodb tablespace。
说明
在测试环境下没有设置过多的详细参数就初始化并启动了服务，后期优化的过程中发现innodb_data_file_path设置过小：
[email protected] 14:59: [(none)]> show variables like '%innodb_data_file_path%';
+-----------------------+------------------------+
| Variable_name | Value |
+-----------------------+------------------------+
| innodb_data_file_path | ibdata1:12M:autoextend |
+-----------------------+------------------------+
1 row in set (0.00 sec)
[email protected] 14:59: [(none)]>
当没有配置innodb_data_file_path时，默认innodb_data_file_path = ibdata1:12M:autoextend
[mysqld]
innodb_data_file_path = ibdata1:12M:autoextend
当需要改为1G时，不能直接在配置文件把 ibdata1 改为 1G ,
[mysqld]
innodb_data_file_path = ibdata1:1G:autoextend
否则启动服务之后，从错误日志看到如下报错：
大致意思就是ibdata1的大小不是 65536page16KB/1024KB=1G ,而是 786page16KB/1024KB=12M
（未使用压缩页）
方法一：推荐
而应该再添加一个 ibdata2:1G ，如下：
[mysqld]
innodb_data_file_path = ibdata1:12M;ibdata2:1G:autoextend
重启数据库！
方法二：不推荐
直接改为如下的话
[mysqld]
innodb_data_file_path = ibdata1:1G:autoextend
可以删除$mysql_datadir目录下 ibdata1、ib_logfile0、ib_logfile1 文件：
也可以启动MySQL，但是mysql错误日志里会报如下错误：
2019-03-29T07:10:47.844560Z 0 [Warning] Could not increase number of max_open_files to more than 5000 (request: 65535)
2019-03-29T07:10:47.844686Z 0 [Warning] Changed limits: table_open_cache: 1983 (requested 2000)
2019-03-29T07:10:48.028262Z 0 [Warning] 'NO_AUTO_CREATE_USER' sql mode was not set.
2019-03-29T07:10:48.147653Z 0 [Warning] InnoDB: Cannot open table mysql/plugin from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
mysqld: Table 'mysql.plugin' doesn't exist
2019-03-29T07:10:48.147775Z 0 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
2019-03-29T07:10:48.163444Z 0 [Warning] InnoDB: Cannot open table mysql/gtid_executed from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
mysqld: Table 'mysql.gtid_executed' doesn't exist
2019-03-29T07:10:48.163502Z 0 [Warning] Gtid table is not ready to be used. Table 'mysql.gtid_executed' cannot be opened.
2019-03-29T07:10:48.163658Z 0 [Warning] InnoDB: Cannot open table mysql/gtid_executed from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
mysqld: Table 'mysql.gtid_executed' doesn't exist
2019-03-29T07:10:48.163711Z 0 [Warning] Gtid table is not ready to be used. Table 'mysql.gtid_executed' cannot be opened.
2019-03-29T07:10:48.164619Z 0 [Warning] Failed to set up SSL because of the following SSL library error: SSL context is not usable without certificate and private key
2019-03-29T07:10:48.166805Z 0 [Warning] InnoDB: Cannot open table mysql/server_cost from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
2019-03-29T07:10:48.166891Z 0 [Warning] Failed to open optimizer cost constant tables
2019-03-29T07:10:48.168072Z 0 [Warning] InnoDB: Cannot open table mysql/time_zone_leap_second from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
2019-03-29T07:10:48.168165Z 0 [Warning] Can't open and lock time zone table: Table 'mysql.time_zone_leap_second' doesn't exist trying to live without them
2019-03-29T07:10:48.169454Z 0 [Warning] InnoDB: Cannot open table mysql/servers from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
2019-03-29T07:10:48.169527Z 0 [ERROR] Can't open and lock privilege tables: Table 'mysql.servers' doesn't exist
2019-03-29T07:10:48.170042Z 0 [Warning] InnoDB: Cannot open table mysql/slave_master_info from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
2019-03-29T07:10:48.170617Z 0 [Warning] InnoDB: Cannot open table mysql/slave_relay_log_info from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
2019-03-29T07:10:48.170946Z 0 [Warning] InnoDB: Cannot open table mysql/slave_master_info from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
2019-03-29T07:10:48.171046Z 0 [Warning] Info table is not ready to be used. Table 'mysql.slave_master_info' cannot be opened.
2019-03-29T07:10:48.171272Z 0 [Warning] InnoDB: Cannot open table mysql/slave_worker_info from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
2019-03-29T07:10:48.171626Z 0 [Warning] InnoDB: Cannot open table mysql/slave_relay_log_info from the internal data dictionary of InnoDB though the .frm file for the table exists. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.
2019-03-29T07:10:48.171688Z 0 [Warning] Info table is not ready to be used. Table 'mysql.slave_relay_log_info' cannot be opened.
关于innodb_data_file_path设置（扩展）
innodb_data_file_path用来指定innodb tablespace文件，如果我们不在My.cnf文件中指定innodb_data_home_dir和innodb_data_file_path那么默认会在datadir目录下创建ibdata1 作为innodb tablespace。5.6.6之后 两个参数的默认值如下：
show variables like ‘innodb_data%’;
±----------------------±-----------------------+
| Variable_name | Value |
±----------------------±-----------------------+
| innodb_data_file_path | ibdata1:12M:autoextend |
| innodb_data_home_dir | | >>note：虽然不指定innodb_data_home_dir和指定它为空显示是一样的，但是作用确不一样，如果不指定那么所有的innodb tablespace 文件只能存放在datadir目录下。如果显示指定为空，则可以为innodb tablespace 文件指定不同的路径
自mysql 5.6.6开始我们可以指定多个innodb tablespace 文件(这些文件可以在相同的路径下，也可以在不同的路径下)。但是在为innodb_data_file_path 指定多个文件时还是有许多注意事项的，下面我来看一下
- 在同一个路径下指定多个innodb tablespace 文件
在my.cnf文件指定如下
[mysqld]
innodb_data_file_path = ibdata1:1G;ibdata2:12M:autoextend:max:500M
note：The autoextend and max attributes can be used only for the last data file in the innodb_data_file_path line.
note：因为没有指定innodb_data_home_dir，所以ibdata1和ibdata2都在datadir(innodb_data_home_dir默认值为datadir)目录下创建
在my.cnf文件指定如下
[mysqld]
innodb_data_home_dir = /data/mysql/mysql3306/data
innodb_data_file_path = ibdata1:1G;ibdata2:12M:autoextend:max:500M
note：可以显示的指定innodb tablespace文件的路径，如果指定innodb_data_home_dir，那么就不能为innodb tablespace不同文件指定不同路径
-
在不同路径下指定innodb tablespace
在my.cnf文件下指定
[mysqld]
innodb_data_home_dir =
innodb_data_file_path = ibdata1:12M;/data/mysql/mysql3306/data1/ibdata2:12M:autoextend
note：如果想为innodb tablespace指定不同目录下的文件，必须指定innodb_data_home_dir =。这个例子中会在datadir下建立ibdata1，在/data/mysql/mysql3306/data1/目录下创建ibdata2
如果我不指定innodb_data_home_dir =，只在my.cnf文件中做如下指定：
innodb_data_file_path = ibdata1:12M;/data/mysql/mysql3306/data1/ibdata2:12M:autoextend
然后使用该my.cnf文件进行数据库初始化的时候，会发现初始化失败，报错如下：
##所以如果想为innodb tablespace文件指定不同路径，那么必须在my.cnf文件中指定innodb_data_home_dir =