Skip to content

Create an incremental backup

xtrabackup supports incremental backups, which means that they can copy only all the data that has changed since the last backup.

Note

Incremental backups on the MyRocks storage engine do not determine if an earlier full backup or incremental backup contains the same files. Percona XtraBackup copies all the MyRocks files each time it takes a backup.

You can perform many incremental backups between each full backup, so you can set up a backup process such as a full backup once a week and an incremental backup every day, or full backups every day and incremental backups every hour.

Incremental backups work because each InnoDB page contains a log sequence number, or LSN. The LSN is the system version number for the entire database. Each page’s LSN shows how recently it was changed.

An incremental backup copies each page which LSN is newer than the previous incremental or full backup’s LSN. An algorithm finds the pages that match the criteria. The algorithm reads the data pages and checks the page LSN.

Create an incremental backup

To make an incremental backup, begin with a full backup as usual. The xtrabackup binary writes a file called xtrabackup_checkpoints into the backup’s target directory. This file contains a line showing the to_lsn, which is the database’s LSN at the end of the backup. Create the full backup with a following command:

$ xtrabackup --backup --target-dir=/data/backups/base

If you look at the xtrabackup_checkpoints file, you should see similar content depending on your LSN nuber:

Expected output
backup_type = full-backuped
from_lsn = 0
to_lsn = 1626007
last_lsn = 1626007
compact = 0
recover_binlog_info = 1

Now that you have a full backup, you can make an incremental backup based on it. Use the following command:

$ xtrabackup --backup --target-dir=/data/backups/inc1 \
--incremental-basedir=/data/backups/base

The /data/backups/inc1/ directory should now contain delta files, such as ibdata1.delta and test/table1.ibd.delta. These represent the changes since the LSN 1626007. If you examine the xtrabackup_checkpoints file in this directory, you should see similar content to the following:

Expected output
backup_type = incremental
from_lsn = 1626007
to_lsn = 4124244
last_lsn = 4124244
compact = 0
recover_binlog_info = 1

from_lsn is the starting LSN of the backup and for incremental it has to be the same as to_lsn (if it is the last checkpoint) of the previous/base backup.

It’s now possible to use this directory as the base for yet another incremental backup:

$ xtrabackup --backup --target-dir=/data/backups/inc2 \
--incremental-basedir=/data/backups/inc1

This folder also contains the xtrabackup_checkpoints:

Expected output
backup_type = incremental
from_lsn = 4124244
to_lsn = 6938371
last_lsn = 7110572
compact = 0
recover_binlog_info = 1

Note

In this case you can see that there is a difference between the to_lsn (last checkpoint LSN) and last_lsn (last copied LSN), this means that there was some traffic on the server during the backup process.

Next step

Prepare the backup

Get expert help

If you need assistance, visit the community forum for comprehensive and free database knowledge, or contact our Percona Database Experts for professional support and services.


Last update: 2024-06-12