Innodb_log_file_size

http://www.mysqlperformanceblog.com/2008/11/21/how-to-calculate-a-good-innodb-log-file-size/

Change innodb_log_file_size with out effect of existing innodb tables

Changing innodb_log_file_size of MySQL-Server.

Steps to change  innodb_log_file_size without effecting of existing innodb tables's data.
1. Check innodb_fast_shutdown value in server variables. It is global variable. Before changing innodb_log_file_size, You have to set innodb_fast_shutdown = 0 or OFF.
2. Stop MySQL server.
3. Delete innodb log files.
4. Start MySQL server.


Setting of innodb_fast_shutdown=0 takes little time, to purge all data.

InnoDB-Buffer Pool Size

1. We have to check RAM and ,  You can set .._buffer_pool_size up to 50 - 80 %  of RAM but beware of setting memory usage too high