5.1 Preparing the Backup to be Restored

Immediately after the backup job completes, the backup files might not be in a consistent state, because data could be inserted, updated, or deleted while the backup is running. These initial backup files are known as the raw backup. You must update the backup files so that they reflect the state of the database corresponding to a specific InnoDB log sequence number (the same kind of operation takes place during a crash recovery). When this step is complete, these final files are known as the prepared backup.

During the backup, mysqlbackup copies the accumulated InnoDB log to a file called ibbackup_logfile. This log file is used to “roll forward” the backed-up data files, so that every page in the data files corresponds to the same log sequence number of the InnoDB log. This phase also creates new ib_logfiles that correspond to the data files.

The mysqlbackup option for turning a raw backup into a prepared backup is apply-log. You can run this step on the same database server where you did the backup, or transfer the raw backup files to a different system first, to limit the CPU and storage overhead on the database server.

Note

Since the apply-log operation does not modify any of the original files in the backup, nothing is lost if the operation fails for some reason (for example, insufficient disk space). After fixing the problem, you can safely retry apply-log and by specifying the --force option, which allows the data and log files created by the failed apply-log operation to be overwritten.

For simple directory backups (which are not compressed and non-incremental), you can combine the initial backup and the apply-log steps using the backup-and-apply-log command.

You can also perform apply-log and copy-back (which restores the prepared backup) with a single copy-back-and-apply-log command.

Example 5.1 Applying the Log to a Backup

This example runs mysqlbackup to roll forward the data files so that the data is ready to be restored:

mysqlbackup --backup-dir=/export/backups/2011-06-21__8-36-58 apply-log

That command creates InnoDB log files (ib_logfile*) within the backup directory and applies log records to the InnoDB data files (ibdata* and *.ibd).

Example 5.2 Applying the Log to a Compressed Backup

If the backup is compressed, as in Section 4.3.3, “Making a Compressed Backup”, specify the --uncompress option to mysqlbackup when applying the log to the backup:

mysqlbackup --backup-dir=/export/backups/compressed --uncompress apply-log

Example 5.3 Applying an Incremental Backup to a Full Backup

After you take an incremental backup as described in Section 4.3.2, “Making a Differential or Incremental Backup”, the changes reflected in those backup files must be applied to a full backup to bring the full backup up-to-date, in the same way that you apply changes from the binary log.

To bring the data files from the full backup up to date, first run the apply log step so that the data files will include any changes that occurred while the full backup was running. Then apply the changes from the incremental backup to the data files produced by the full backup:

mysqlbackup --backup-dir=/export/backups/full apply-log
mysqlbackup --backup-dir=/export/backups/full \
  --incremental-backup-dir=/export/backups/incremental \
  apply-incremental-backup

Now the data files in the full-backup directory are fully up-to-date as of the time of the incremental backup.