CPU Usage 100% - Backups Complete?

When running the daily backup the CPU Usage hits 100% and then returns to normal (usually it hovers between of 0% and 25%).

When it hits 0% will the backup complete successfully? Or, will it cause an error in the backup?

Is this something that others notice when running a backup?

This is on a Linode 4GB 2 Cores with 6 small WordPress sites, 1 WooCommerce site, and 3 small PHP sites.