119 lines
3.1 KiB
ReStructuredText
119 lines
3.1 KiB
ReStructuredText
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Terminology
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===========
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Backup Content
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--------------
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When doing deduplication, there are different strategies to get
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optimal results in terms of performance and/or deduplication rates.
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Depending on the type of data, it can be split into *fixed* or *variable*
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sized chunks.
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Fixed sized chunking requires minimal CPU power, and is used to
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backup virtual machine images.
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Variable sized chunking needs more CPU power, but is essential to get
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good deduplication rates for file archives.
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The Proxmox Backup Server supports both strategies.
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Image Archives: ``<name>.img``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This is used for virtual machine images and other large binary
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data. Content is split into fixed-sized chunks.
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File Archives: ``<name>.pxar``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.. see https://moinakg.wordpress.com/2013/06/22/high-performance-content-defined-chunking/
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A file archive stores a full directory tree. Content is stored using
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the :ref:`pxar-format`, split into variable-sized chunks. The format
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is optimized to achieve good deduplication rates.
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Binary Data (BLOBs)
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~~~~~~~~~~~~~~~~~~~
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This type is used to store smaller (< 16MB) binary data such as
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configuration files. Larger files should be stored as image archive.
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.. caution:: Please do not store all files as BLOBs. Instead, use the
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file archive to store whole directory trees.
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Catalog File: ``catalog.pcat1``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The catalog file is an index for file archives. It contains
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the list of files and is used to speed up search operations.
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The Manifest: ``index.json``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The manifest contains the list of all backup files, their
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sizes and checksums. It is used to verify the consistency of a
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backup.
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Backup Type
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-----------
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The backup server groups backups by *type*, where *type* is one of:
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``vm``
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This type is used for :term:`virtual machine`\ s. Typically
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consists of the virtual machine's configuration file and an image archive
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for each disk.
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``ct``
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This type is used for :term:`container`\ s. Consists of the container's
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configuration and a single file archive for the filesystem content.
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``host``
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This type is used for backups created from within the backed up machine.
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Typically this would be a physical host but could also be a virtual machine
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or container. Such backups may contain file and image archives, there are no restrictions in this regard.
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Backup ID
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---------
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A unique ID. Usually the virtual machine or container ID. ``host``
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type backups normally use the hostname.
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Backup Time
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-----------
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The time when the backup was made.
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Backup Group
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------------
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The tuple ``<type>/<ID>`` is called a backup group. Such a group
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may contain one or more backup snapshots.
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Backup Snapshot
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---------------
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The triplet ``<type>/<ID>/<time>`` is called a backup snapshot. It
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uniquely identifies a specific backup within a datastore.
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.. code-block:: console
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:caption: Backup Snapshot Examples
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vm/104/2019-10-09T08:01:06Z
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host/elsa/2019-11-08T09:48:14Z
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As you can see, the time format is RFC3399_ with Coordinated
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Universal Time (UTC_, identified by the trailing *Z*).
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