Services fail when backups start

Hello, I have put in WHM to start backup (compressed) "Daily" at 2 am. I have noticed that before backup starts, my services: sshd, dovecot, httpd, mysqld, named, exim, pure-authd was down at 1:59am, and was up at 2:04am. Backup process was sucesuffully complited after 8min. Why is this happening? Best regards, Elizabeta