Last checkpoint at ：redo log記錄的更新已經(jīng)刷新到磁盤上的檢查點LSN，該LSN之前的redo log上記錄的更新已全部刷新到磁盤上，可以被覆蓋重復使用。
7、查看ib_logfile里的內容的方法
[root@mydb ~]# strings /var/lib/mysql/ib_logfile0
相關參數(shù)
innodb_log_file_size ：每個redo log文件大小
innodb_log_files_in_group ：redo log日志組成員個數(shù)
innodb_log_group_home_dir ：redo log存放目錄
innodb_page_size ：InnoDB表空間的頁面大小，默認16K
innodb_flush_log_at_timeout ：日志刷新頻率，單位秒
Write and flush the logs every N seconds. innodb_flush_log_at_timeout allows the timeout period between flushes to be increased in order to reduce flushing and avoid impacting performance of binary log group commit. The default setting for innodb_flush_log_at_timeout is once per second.
By default, the redo log is physically represented on disk as a set of files, named ib_logfile0 and ib_logfile1. MySQL writes to the redo log files in a circular fashion.
A disk-based data structure used during crash recovery, to correct data written by incomplete transactions. During normal operation, it encodes requests to change InnoDB table data, which result from SQL statements or low-level API calls through NoSQL interfaces. Modifications that did not finish updating the data files before an unexpected shutdown are replayed automatically.
The redo log is physically represented as a set of files, typically named ib_logfile0 and ib_logfile1. The data in the redo log is encoded in terms of records affected; this data is collectively referred to as redo. The passage of data through the redo logs is represented by the ever-increasing LSN value. The original 4GB limit on maximum size for the redo log is raised to 512GB in MySQL 5.6.3.
