How to limit CPU consumption during backup in ISP Manager Lite 4?

Question

Backup

Through the ISP Manager panel, under root, backup of user files and mysql databases is configured. About 100 domains, about 200Gb.
During the execution of the task, the sites go into a 504 error, because. not enough resources.
How to limit the CPU load of the backup process? The execution time is not critical. Let it hang in the background at least constantly.

Answer 1

man renice?
+ ionice