The purpose of this article is to provide a step-by-step guide on how you could potentially increase the speed of your nightly cPanel backups.
If your server uses compressed backups, there are several settings within WHM > Tweak Settings > Compression that you can customize to speed up backups:
cPanel Documentation: Tweak Settings » Compression
You could also adjust the I/O priority of backups via Tweak Settings in WHM. A low number for the following setting would allow backups to complete faster:
I/O priority level at which nightly backups are run (Minimum: 0; Maximum: 7) [?]
Lastly, if you are taking compressed backups, you could instead take uncompressed backups. The drawback to this would be that your backups will consume more disk space. This setting can be changed from within the Backup Configuration interface in WHM.