---quote---
jbd is the journaling layer which ext3 uses. One of the things that
the jbd layer does is to batch updates to the disk into compound
atomic transactions, and those are written to disk in the background. kjournald is the name of the thread that the jbd code creates to perform those background commits.
---end-quote---
You cannot stop kjournald process. It is ran by the kernel itself. If you see kjournald and kupdated using too much CPU, it means there is a lot of data that is being written to the disks. Maybe a lot of FTP users uploading their site content? Huge number of domains which each will write their own logfile in the server?
Tip

:
Disabling ATIME i.e using noatime on fstab will save a lot of i/o which inturn decreases the load from kjournald/kupdated
Regarding disabling CPanel backup, how cpanel backups is that it can recreate all the settings when doing a restore. If you just need the data part, then you can disable cpanel backup and use your own. Else, you can disable your own backup and let cpanel backup it's content.
Hope this helps
