Symptoms

Ploop container consumes significantly more disk space on the server, than the data size inside it:

[root@vz ~]# du -h /vz/private/101/root.hdd/root.hds
154G    /vz/private/101/root.hdd/root.hds

[root@vz ~]# vzctl enter 101
entered into Container 101
CT-101-bash-4.1# df -h
Filesystem         Size  Used Avail Use% Mounted on
/dev/ploop18346p1  197G   62G  133G  32% /
none               1.0G  4.0K  1.0G   1% /dev

Cause

Depending on the data structure inside a container, a scheduled daily job that compacts ploop images automatically, /etc/cron.d/pcompact, might not be effective. One of the possible reasons of such behavior is high fragmentation level inside a container.

Resolution

There are few methods to compact a container manually.

• Truncate unused blocks with the help of prl_disk_tool utility on stopped container:

  # prl_disk_tool compact --hdd /vz/private/101/root.hdd/
  

• Downsize stopped container and upsize it back to the original value:

  # vzctl stop 101
  # prl_disk_tool resize --hdd /vz/private/101/root.hdd --size 75000M
  # prl_disk_tool resize --hdd /vz/private/101/root.hdd --size 199000M