Incremental backups of MySQL, specifically for the InnoDB engine, are taken by copying modified pages from the previous backup. The brute force method takes backups by scanning every page in tablespace file in the server data directory is an expensive operation. The time required for incremental backups increases as the data-dir size increases. To solve this [&]

https://www.percona.com/blog/incremental-backup-in-mysql-using-page-tracking/