Article ID: 122262, created on Jul 6, 2014, last review on Jun 17, 2016

  • Applies to:
  • Virtuozzo 6.0


Disk image snapshots for containers can be created for internal purposes, like backup creation or online migration.

Such snapshots are temporary and should be merged back automatically upon finishing the operation: after backup is created or if the operation is failed, after migrating of the container is completed or canceled.

However, there are situations when such temporary snapshots are not merged back properly (node reboot/crash, errors in software...), and this results in growing number of snapshots and increasing of disk usage.

This feature introduces new snapshot entity 'temporary snapshot'. Temporary snapshot will auto merged if detected as not used on:

  • disk image mount (as a part of the container's start);
  • create snapshot (both persistent or temporary).

Note: Merging of a snapshot on mount/start can take significant amount of time (depending on its size), thus the container can be irresponsive during this period.


This feature has been implemented in Parallels Cloud Server 6.0 Update 6 in the scope of the internal request PSBM-24727.

To merge orphaned snapshots in earlier version of Parallels Cloud Server, follow the instructions from the article KB #118238.

Search Words

disk space

snapshot auto-merge

ploop snapshots found without a cause



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