1. 环境说明

RHEL 6.4 x86_64 + MySQL 5.5.37和MySQL 5.6.19

blog地址：http://blog.csdn.net/hw_libo/article/details/39215723

2. 案例：redo log文件（ib_logfile）大小参数被修改：innodb_log_file_size

innodb_log_file_size = 256M -- 修改为200M

版本是5.5的，启动失败，会出现如下错误：

InnoDB: Error: log file ./ib_logfile0 is of different size 0 268435456 bytes  ## 原来redo log的大小
InnoDB: than specified in the .cnf file 0 209715200 bytes!   ## redo log被修改的大小
140912  0:01:12 [ERROR] Plugin 'InnoDB' init function returned error.
140912  0:01:12 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
140912  0:01:12 [ERROR] Unknown/unsupported storage engine: InnoDB
140912  0:01:12 [ERROR] Aborting

版本是5.6.16之后的，正常启动，会自动将原来的redo log删除，然后重新生成新的redo log（这个比较重要）：

2014-09-11 21:57:05 1093 [Warning] InnoDB: Resizing redo log from 2*16384 to 2*12800 pages, LSN=71249171
2014-09-11 21:57:05 1093 [Warning] InnoDB: Starting to delete and rewrite log files.    ## 删除原redo log
2014-09-11 21:57:05 1093 [Note] InnoDB: Setting log file ./ib_logfile101 size to 200 MB
InnoDB: Progress in MB: 100 200
2014-09-11 21:57:06 1093 [Note] InnoDB: Setting log file ./ib_logfile1 size to 200 MB
InnoDB: Progress in MB: 100 200
2014-09-11 21:57:07 1093 [Note] InnoDB: Renaming log file ./ib_logfile101 to ./ib_logfile0
2014-09-11 21:57:07 1093 [Warning] InnoDB: New log files created, LSN=71249171   ## 新redo log重建完毕

原redo log大小：2*16384*8(page的大小为8k)/1024=256MB

新redo log大小：2*12800*8/1024=200MB

3. 案例：ibdata1文件大小参数被修改：innodb_data_file_path

（1）ibdata1从大改小

innodb_data_file_path = ibdata1:1G:autoextend -- 修改为：ibdata1:300M:autoextend

在版本是5.5和5.6中，启动正常，并且日志中没有任何异常。但是如果将autoextend去掉，就会报错，启动失败，如：[版本：5.5.37]

InnoDB: Error: data file ./ibdata1 is of a different size
InnoDB: 65536 pages (rounded down to MB)
InnoDB: than specified in the .cnf file 19200 pages!
140911 23:51:53 InnoDB: Could not open or create data files.
140911 23:51:53 InnoDB: If you tried to add new data files, and it failed here,
140911 23:51:53 InnoDB: you should now edit innodb_data_file_path in my.cnf back
140911 23:51:53 InnoDB: to what it was, and remove the new ibdata files InnoDB created
140911 23:51:53 InnoDB: in this failed attempt. InnoDB only wrote those files full of
140911 23:51:53 InnoDB: zeros, but did not yet use them in any way. But be careful: do not
140911 23:51:53 InnoDB: remove old data files which contain your precious data!
140911 23:51:53 [ERROR] Plugin 'InnoDB' init function returned error.
140911 23:51:53 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
140911 23:51:53 [ERROR] Unknown/unsupported storage engine: InnoDB
140911 23:51:53 [ERROR] Aborting

原来的ibdata1大小为：65536*8*2/1024=1024M=1G
当前ibdata1被修改为：19200*8*2/1024=300M

（2）ibdata1值小改大

比如：

innodb_data_file_path = ibdata1:1G:autoextend -- 修改为：ibdata1:1200M:autoextend

那么会在启动时出现如下错误：

*****在5.5版本中：[版本：5.5.37]

InnoDB: Error: auto-extending data file ./ibdata1 is of a different size
InnoDB: 65536 pages (rounded down to MB) than specified in the .cnf file:
InnoDB: initial 76800 pages, max 0 (relevant if non-zero) pages!
140911 23:57:43 InnoDB: Could not open or create data files.
140911 23:57:43 InnoDB: If you tried to add new data files, and it failed here,
140911 23:57:43 InnoDB: you should now edit innodb_data_file_path in my.cnf back
140911 23:57:43 InnoDB: to what it was, and remove the new ibdata files InnoDB created
140911 23:57:43 InnoDB: in this failed attempt. InnoDB only wrote those files full of
140911 23:57:43 InnoDB: zeros, but did not yet use them in any way. But be careful: do not
140911 23:57:43 InnoDB: remove old data files which contain your precious data!
140911 23:57:43 [ERROR] Plugin 'InnoDB' init function returned error.
140911 23:57:43 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
140911 23:57:43 [ERROR] Unknown/unsupported storage engine: InnoDB
140911 23:57:43 [ERROR] Aborting

*****在5.6版本中：[版本：5.6.19]

2014-09-11 22:20:01 1222 [ERROR] InnoDB: auto-extending data file ./ibdata1 is of a different size 65536 pages (rounded down to MB) than
 specified in the .cnf file: initial 76800 pages, max 0 (relevant if non-zero) pages!
2014-09-11 22:20:01 1222 [ERROR] InnoDB: Could not open or create the system tablespace. If you tried to add new data files to the syste
m 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 ibdata fil
es 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 caref
ul: do not remove old data files which contain your precious data!
2014-09-11 22:20:01 1222 [ERROR] Plugin 'InnoDB' init function returned error.
2014-09-11 22:20:01 1222 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2014-09-11 22:20:01 1222 [ERROR] Unknown/unsupported storage engine: InnoDB
2014-09-11 22:20:01 1222 [ERROR] Aborting

原来的ibdata1大小为：65536*8*2/1024=1024M=1G

当前ibdata1被修改为：76800*8*2/1024=1200M

blog地址：http://blog.csdn.net/hw_libo/article/details/39215723

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