I have a similar problem. I added a new account the other day (normally I have just my own) and added some websites that took up about 1/2 gig of space. The next day I saw 25 gig of space get used, so I doubled the size of the drive. I then found today that the server had doubled in size again, and from being only 30 gig is now 80 gig.
The reason is the creation of the files in the backup directory under the
/ backup / weekly / user / backupcwp / directory.
My own sites are not being backuped like this, they only backup the code and are smaller.
What is the backupupcwp directory for? It has a tar file in it of 10 gig, and it is creating a new one in the daily backup, weekly backup and monthly backup. If I do not delete them they will take up 10gig x 7 in the daily backup alone, which is 3 times the size fo the rest of the server!
How do I stop it creating these backups, it never used to do this, and what are they for?