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init: Add --copy-chunker-params option

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This allows creating multiple repositories with identical chunker
parameters which is required for working deduplication when copying
snapshots between different repositories.
This commit is contained in:
Michael Eischer
2020-09-19 12:41:52 +02:00
parent 655430550b
commit f003410402
6 changed files with 114 additions and 9 deletions
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doc/045_working_with_repos.rst
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@@ -110,7 +110,8 @@ be skipped by later copy runs.
entire snapshot(s) due to the different encryption keys used in the source and
destination repository. Also, the transferred files are not re-chunked, which
may break deduplication between files already stored in the destination repo
and files copied there using this command.
and files copied there using this command. See the next section for how to avoid
this problem.
For the destination repository ``--repo2`` the password can be read from
a file ``--password-file2`` or from a command ``--password-command2``.
@@ -142,6 +143,28 @@ which case only these instead of all snapshots will be copied:
$ restic -r /srv/restic-repo copy --repo2 /srv/restic-repo-copy 410b18a2 4e5d5487 latest
Ensuring deduplication for copied snapshots
-------------------------------------------
Even though the copy command can transfer snapshots between arbitrary repositories,
deduplication between snapshots from the source and destination repository may not work.
To ensure proper deduplication, both repositories have to use the same parameters for
splitting large files into smaller chunks, which requires additional setup steps. With
the same parameters restic will for both repositories split identical files into
identical chunks and therefore deduplication also works for snapshots copied between
these repositories.
The chunker parameters are generated once when creating a new (destination) repository.
That is for a copy destination repository we have to instruct restic to initialize it
using the same chunker parameters as the source repository:
.. code-block:: console
$ restic -r /srv/restic-repo-copy init --repo2 /srv/restic-repo --copy-chunker-params
Note that it is not possible to change the chunker parameters of an existing repository.
Checking integrity and consistency
==================================