mysql中redo log是什么

root@test:/var/lib/mysql# pwd

/var/lib/mysql

root@test:/var/lib/mysql# ls -lstr ib_logfile*

49152 -rw-r----- 1 mysql mysql 50331648 Dec 28 15:45 ib_logfile1

49152 -rw-r----- 1 mysql mysql 50331648 Jan  3 12:53 ib_logfile0

root@test:/var/lib/mysql# du -sh ib_logfile*

48M ib_logfile0

48M ib_logfile1

root@test:/var/lib/mysql#