When compacting GPT disk with prl_disk_tool the following error message is displayed:
[root@psbm5 ~]# prl_disk_tool resize --size 3000G --hdd /vz/vmprivate/myvm.pvm/harddisk1.hdd/ --resize_partition
The disk could not be resized because there is no enough free space on the last volume.
The issue is known as #PSBM-15936 is actual for Parallels Server Bare Metal 5 update 6 and earlier.
Install all pending updates for Parallels Server Bare Metal 5, including update 7
where the issue was fixed permanently.