There are different commands to backup virtual environments. What is the difference? Are these tools compatible?
tar-based tool supported since Virtuozzo 3.0. The backup can be compressed by
Staring from PVC 4.0, backups can be split to parts with the configurable size.
tarworks with files, and if a file is changed during backup creation, the content of the file can be corrupted from the application point of view.
In PVC 4.0, as a part of Parallels Infrastructure Manager 4.0 (and later, Parallels Virtual Automation 4.5, 4.6 and 6.0), in order to improve backup creation and to avoid situations with storing files which are being changed during backup creation, backups are created using Acronis.
The operation is performed on block level. First, the map of disk blocks used by files of a container is gathered. Second, the content of these disk blocks is put to the archive, with tracking changes in files of the container. Third, the collected changes are put to the archive.
Note: the resulting backup contains the state of the container at the beginning of the third stage. Content of memory buffers of applications is not saved, thus the data might be incomplete still, however this is architectural limitation of Linux backup engine, as there is no common way to inform applications about backup creation.
vzabackupcan be configured to use
vzbackupfor backup creation. The tool
vzbackupsynccan be used to import information about
tarbased backups to PVA Agent database.
In Parallels Cloud Server 6.0, container's private area can be stored in a single file, representing a standalone Ext4 file system. First, a disk snapshot is created: an empty disk image part (a delta) is created and all changes are stored on block level to this delta. Second, the base image (which is not changed since the delta exists to write changes into) is put to an archive (
taror Acronis based, whichever command is used). Third, the delta is merged to the base image once the backup creation is completed.
Note: The resulting backup file contains the container's disk image actual at the moment of a delta creation.
prlctl backup(for containers (PCS and later) and virtual machines (PSBM, PCS and later))
In Parallels Server products, backup operation is controlled by Dispatcher process, which invokes the tool
prl_backup_client, an Acronis-based tool. Backup creation for containers is similar to
vzabackup(but it is not possible to switch backup tool to
vzbackup). A backup for a virtual machine is created in the same way as for a Ploop container, with creating a temporary snapshot for a VM.
Note: Backups, created by
prlctl backup, are not listed by
vzabackuptool and cannot be extracted (PVA-34048). Also, these backups are not listed in PVA interface.
vzabackup(for virtual machines)
vzabackupis a part of PVA Agent installation, which has a special component to communicate with the Dispatcher process. Therefore, backups of virtual machines are created by the same function used by
prlctl backupand such backups are fully manageable by both tools,
prlctl backup. As the result, these backups are visible in PVA interface.
This tool is an extension for
tarfor containers and
prlctl backupfor virtual machines.
In Windows versions (VZ 3.5, PVC 4.0, 4.5, 4.6, PCW 6.0), the commands
vzabackup are aliases, this is the same Acronis-based tool.
First, VSS is started in a container. Second, the disk image is saved to a backup. Third, VSS is stopped in the container.