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1 | Terminology |
2 | =========== | |
3 | ||
4 | Backup Content | |
5 | -------------- | |
6 | ||
7 | When doing deduplication, there are different strategies to get | |
8 | optimal results in terms of performance and/or deduplication rates. | |
9 | Depending on the type of data, it can be split into *fixed* or *variable* | |
10 | sized chunks. | |
11 | ||
12 | Fixed sized chunking requires minimal CPU power, and is used to | |
13 | backup virtual machine images. | |
14 | ||
15 | Variable sized chunking needs more CPU power, but is essential to get | |
16 | good deduplication rates for file archives. | |
17 | ||
18 | The Proxmox Backup Server supports both strategies. | |
19 | ||
20 | ||
21 | Image Archives: ``<name>.img`` | |
22 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
23 | ||
24 | This is used for virtual machine images and other large binary | |
25 | data. Content is split into fixed-sized chunks. | |
26 | ||
27 | ||
28 | File Archives: ``<name>.pxar`` | |
29 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
30 | ||
31 | .. see https://moinakg.wordpress.com/2013/06/22/high-performance-content-defined-chunking/ | |
32 | ||
33 | A file archive stores a full directory tree. Content is stored using | |
34 | the :ref:`pxar-format`, split into variable-sized chunks. The format | |
35 | is optimized to achieve good deduplication rates. | |
36 | ||
37 | ||
38 | Binary Data (BLOBs) | |
39 | ~~~~~~~~~~~~~~~~~~~ | |
40 | ||
41 | This type is used to store smaller (< 16MB) binary data such as | |
42 | configuration files. Larger files should be stored as image archive. | |
43 | ||
44 | .. caution:: Please do not store all files as BLOBs. Instead, use the | |
45 | file archive to store whole directory trees. | |
46 | ||
47 | ||
48 | Catalog File: ``catalog.pcat1`` | |
49 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
50 | ||
51 | The catalog file is an index for file archives. It contains | |
52 | the list of files and is used to speed up search operations. | |
53 | ||
54 | ||
55 | The Manifest: ``index.json`` | |
56 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
57 | ||
58 | The manifest contains the list of all backup files, their | |
59 | sizes and checksums. It is used to verify the consistency of a | |
60 | backup. | |
61 | ||
62 | ||
63 | Backup Type | |
64 | ----------- | |
65 | ||
66 | The backup server groups backups by *type*, where *type* is one of: | |
67 | ||
68 | ``vm`` | |
69 | This type is used for :term:`virtual machine`\ s. Typically | |
70 | consists of the virtual machine's configuration file and an image archive | |
71 | for each disk. | |
72 | ||
73 | ``ct`` | |
74 | This type is used for :term:`container`\ s. Consists of the container's | |
75 | configuration and a single file archive for the filesystem content. | |
76 | ||
77 | ``host`` | |
78 | This type is used for backups created from within the backed up machine. | |
79 | Typically this would be a physical host but could also be a virtual machine | |
80 | or container. Such backups may contain file and image archives, there are no restrictions in this regard. | |
81 | ||
82 | ||
83 | Backup ID | |
84 | --------- | |
85 | ||
86 | A unique ID. Usually the virtual machine or container ID. ``host`` | |
87 | type backups normally use the hostname. | |
88 | ||
89 | ||
90 | Backup Time | |
91 | ----------- | |
92 | ||
93 | The time when the backup was made. | |
94 | ||
95 | ||
96 | Backup Group | |
97 | ------------ | |
98 | ||
99 | The tuple ``<type>/<ID>`` is called a backup group. Such a group | |
100 | may contain one or more backup snapshots. | |
101 | ||
102 | ||
103 | Backup Snapshot | |
104 | --------------- | |
105 | ||
106 | The triplet ``<type>/<ID>/<time>`` is called a backup snapshot. It | |
107 | uniquely identifies a specific backup within a datastore. | |
108 | ||
109 | .. code-block:: console | |
110 | :caption: Backup Snapshot Examples | |
111 | ||
112 | vm/104/2019-10-09T08:01:06Z | |
113 | host/elsa/2019-11-08T09:48:14Z | |
114 | ||
115 | As you can see, the time format is RFC3399_ with Coordinated | |
116 | Universal Time (UTC_, identified by the trailing *Z*). | |
117 | ||
118 |