Throttling Backups

Although xtrabackup does not block your database’s operation, any backup can add load to the system being backed up. On systems that do not have much spare I/O capacity, it might be helpful to throttle the rate at which xtrabackup reads and writes data. You can do this with the --throttle option. This option limits the number of chunks copied per second. The chunk +size is 10 MB.

The image below shows how throttling works when --throttle is set to 1.

../_images/throttle.png

When specified with the --backup option, this option limits the number of pairs of read-and-write operations per second that xtrabackup will perform. If you are creating an incremental backup, then the limit is the number of read I/O operations per second.

By default, there is no throttling, and xtrabackup reads and writes data as quickly as it can. If you set too strict of a limit on the IOPS, the backup might be so slow that it will never catch up with the transaction logs that InnoDB is writing, so the backup might never complete.