While searching various forums, posting & chatting, I have realized that many VPS providers are having issues with their quotas on their VPS plans. If your clients cannot set specific disk space limits, and everything shows as unlimited than second level quotas are not enabled. Here is a small tutorial on how to do this.
1. Login into the host-node.
2. Find the CTID of the VPS that is having the quota problem.
3. To enter that specific VPS input this command into SSH. Remember to change the CTID with the # from that specific VPS.
4. Once in the configuration file, under “# Disk quota parameters” add this line:
5. Click CTRL + X then Y to save the file and then ENTER.
6. Restart the VPS.
7. Go back in the VPS again and run these two commands.
This will fix the quota issue your client(s) are having. If you have any questions feel free to post in the comments.