Ideally, innodb_log_file_size should be to a high enough value to accommodate an increase in server workload activity and optimize write I/O, while not being so large as to inhibit a speedy crash recovery. When recovering from a crash, you can expect roughly 5 minutes per 1GB of innodb_log_file_size. Meaning if your innodb_log_file_size is 3GB, your MySQL server would fully recover in about 15 minutes.
There is an associated variable, innodb_log_files_in_group, but this variable has a default value that is not often changed.
When changing the innodb_log_file_size parameter in MySQL versions befor 5.7, be sure to shut down the server first and move the log files. This will force the server to create new log files. If this is not done, an error concerning log file size mismatch will be thrown:
ERROR 1033 (HY000): Incorrect information in file....