mysqlbackup may sometimes fail to keep pace with redo log generation on the backed up server while a backup operation is in progress, resulting in lost redo log records due to those records being overwritten. This issue most often occurs when there is significant server activity during the backup operation, and the redo log file storage media operates at a faster speed than the backup storage media. The redo log archiving feature addresses this issue by sequentially writing redo log records to an archive file in addition to the redo log files. mysqlbackup can then copy redo log records from the archive file as necessary, thereby avoiding the potential loss of data.
When redo log archiving has been enabled on the server to be backed up, mysqlbackup utilizes the feature by default for backups, as long as the following are true:
The OS user that runs mysqlbackup has read and write access to the folder on the server that stores the redo log archive file; the folder is the first labeled directory defined by the system variable
innodb_redo_log_archive_dirson the server.
The MySQL user mysqlbackup uses to connect to the server must be granted the
INNODB_REDO_LOG_ARCHIVEprivilege, for activating redo log archiving on the server.
Redo log archiving can be skipped using the
If redo log archiving is skipped by mysqlbackup, disabled on the server, or is simply not working for some reasons, mysqlbackup then reverts to copying the redo log data from the redo log files, as it used to do before the feature was introduced.