Consider the following guidelines for optimizing redo logging:
Make your redo log files big, even as big as the buffer pool. When
InnoDBhas written the redo log files full, it must write the modified contents of the buffer pool to disk in a checkpoint. Small redo log files cause many unnecessary disk writes. Although historically big redo log files caused lengthy recovery times, recovery is now much faster and you can confidently use large redo log files.
The size and number of redo log files are configured using the
innodb_log_files_in_groupconfiguration options. For information about modifying an existing redo log file configuration, see Section 14.7.2, “Changing the Number or Size of InnoDB Redo Log Files”.
Consider increasing the size of the log buffer. A large log buffer enables large transactions to run without a need to write the log to disk before the transactions commit. Thus, if you have transactions that update, insert, or delete many rows, making the log buffer larger saves disk I/O. Log buffer size is configured using the
innodb_log_write_ahead_sizeconfiguration option to avoid “read-on-write”. This option defines the write-ahead block size for the redo log. Set
innodb_log_write_ahead_sizeto match the operating system or file system cache block size. Read-on-write occurs when redo log blocks are not entirely cached to the operating system or file system due to a mismatch between write-ahead block size for the redo log and operating system or file system cache block size.
Valid values for
innodb_log_write_ahead_sizeare multiples of the
InnoDBlog file block size (2n). The minimum value is the
InnoDBlog file block size (512). Write-ahead does not occur when the minimum value is specified. The maximum value is equal to the
innodb_page_sizevalue. If you specify a value for
innodb_log_write_ahead_sizethat is larger than the
innodb_log_write_ahead_sizesetting is truncated to the
innodb_log_write_ahead_sizevalue too low in relation to the operating system or file system cache block size results in read-on-write. Setting the value too high may have a slight impact on
fsyncperformance for log file writes due to several blocks being written at once.