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ReStructuredText
46 lines
1.6 KiB
ReStructuredText
.. include:: global.rst.inc
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.. _internals:
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Internals
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=========
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The internals chapter describes and analyses most of the inner workings
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of Borg.
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Borg uses a low-level, key-value store, the :ref:`repository`, and
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implements a more complex data structure on top of it, which is made
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up of the :ref:`manifest <manifest>`, :ref:`archives <archive>`,
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:ref:`items <item>` and data :ref:`chunks`.
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Each repository can hold multiple :ref:`archives <archive>`, which
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represent individual backups that contain a full archive of the files
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specified when the backup was performed.
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Deduplication is performed globally across all data in the repository
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(multiple backups and even multiple hosts), both on data and file
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metadata, using :ref:`chunks` created by the chunker using the
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Buzhash_ algorithm ("buzhash" chunker) or a simpler fixed blocksize
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algorithm ("fixed" chunker).
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To actually perform the repository-wide deduplication, a hash of each
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chunk is checked against the :ref:`chunks cache <cache>`, which is a
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hash-table of all chunks that already exist.
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.. figure:: internals/structure.png
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:figwidth: 100%
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:width: 100%
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Layers in Borg. On the very top commands are implemented, using
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a data access layer provided by the Archive and Item classes.
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The "key" object provides both compression and authenticated
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encryption used by the data access layer. The "key" object represents
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the sole trust boundary in Borg.
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The lowest layer is the repository, either accessed directly
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(Repository) or remotely (RemoteRepository).
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.. toctree::
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:caption: Internals contents
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internals/security
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internals/data-structures
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internals/frontends
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