Basic disk quota management:
To set disk space, run the following commands:
vzctl set CTID --diskspace $SoftLimit$:$HardLimit$ --save
Example:
[host-node]# vzctl set 101 --diskspace 6G:7G --save
You could verify the space available with this command (ie : CTID =101)
[host-node]# vzctl exec 101 df -h
If you want remove disk quota:
DISK_QUOTA=no