If you have already created your database and you change the setting for “innodb_log_file_size=###M” and restart here you database and get an error that looks something like

InnoDB: Error: log file ./ib_logfile0 is of different size 0 5242880 bytes

Here what you need to do.
1.) Make sure your database shutdown clean.
2.) Move(not delete) any existing ib_logfile[#] to a safe place.
3.) edit the “innodb_log_file_size=###M” setting in your my.cnf.
4.) Restart your database and check your log file to make sure there were no errors.
5.) Check to make sure the new ib_logfile[#] are the right size.