Bug #71661 Manual describes InnoDB log limits incorrectly
Submitted: 11 Feb 2014 1:07 Modified: 18 Feb 2014 17:08
Reporter: Jeremy Cole (Basic Quality Contributor) (OCA) Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server: Documentation Severity:S3 (Non-critical)
Version: OS:Any
Assigned to: Daniel Price CPU Architecture:Any

[11 Feb 2014 1:07] Jeremy Cole 
Description:
The MySQL manual for innodb_log_file_size here:

http://dev.mysql.com/doc/refman/5.5/en/innodb-parameters.html#sysvar_innodb_log_file_size

Describes the maximum size for innodb_log_file_size as 4294967295 and the maximum log space as 3.99999999068677 GB. These both are incorrect. Since the manual felt it fit to include a needlessly specific number like 3.99999999068677 GB, I feel it necessary to correct it.

Since the lower limit for innodb_log_files_in_group is 2, and since the log must contain only full 512-byte pages, and since the logs must be exactly equal in size, the actual limit for innodb_log_file_size is (2^32 / 2) - 512 => 2147483136, not 4294967295. This yields a total log space of 2 * 2147483136 => 4294966272. This is 3.99999904632568 GB, not 3.99999999068677, or 1023 bytes less.

I expect this injustice to be corrected.

How to repeat:
Read the documentation.

Suggested fix:
Fix the documentation. Don't make needlessly specific claims unless you're really sure of your maths.
[11 Feb 2014 6:23] MySQL Verification Team 
Hello Jeremy,

Thank you for the bug report.

Thanks,
Umesh
[18 Feb 2014 17:08] Daniel Price 
Posted by developer:
 
The documentation for innodb_log_file_size has been revised for 5.0, 5.1, and 5.5. The documented range value is now documented as Range: 1048576 ... 4GB / innodb_log_files_in_group, similar to how it is documented for 5.6 and 5.7. The parameter description is also updated to reflect the change.

http://dev.mysql.com/doc/refman/5.0/en/innodb-parameters.html#sysvar_innodb_log_file_size
http://dev.mysql.com/doc/refman/5.1/en/innodb-parameters.html#sysvar_innodb_log_file_size
http://dev.mysql.com/doc/refman/5.5/en/innodb-parameters.html#sysvar_innodb_log_file_size

The change should appear soon, with the next published documentation build. 

Thank you for the bug report.