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more details about checkpoints, add split trick, fixes #1171
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docs/faq.rst
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docs/faq.rst
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@ -180,13 +180,53 @@ Yes, |project_name| supports resuming backups.
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During a backup a special checkpoint archive named ``<archive-name>.checkpoint``
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During a backup a special checkpoint archive named ``<archive-name>.checkpoint``
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is saved every checkpoint interval (the default value for this is 5
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is saved every checkpoint interval (the default value for this is 5
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minutes) containing all the data backed-up until that point. This means
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minutes) containing all the data backed-up until that point.
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that at most <checkpoint interval> worth of data needs to be retransmitted
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if a backup needs to be restarted.
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Checkpoints only happen between files (so they don't help for interruptions
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happening while a very large file is being processed).
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This checkpoint archive is a valid archive (all files in it are valid and complete),
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but it is only a partial backup (not all files that you wanted to backup are
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contained in it). Having it in the repo until a successful, full backup is
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completed is useful because it references all the transmitted chunks up
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to the checkpoint. This means that in case of an interruption, you only need to
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retransfer the data since the last checkpoint.
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If a backup was interrupted, you do not need to do any special considerations,
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just invoke ``borg create`` as you always do. You may use the same archive name
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as in previous attempt or a different one (e.g. if you always include the current
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datetime), it does not matter.
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|project_name| always does full single-pass backups, so it will start again
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from the beginning - but it will be much faster, because some of the data was
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already stored into the repo (and is still referenced by the checkpoint
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archive), so it does not need to get transmitted and stored again.
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Once your backup has finished successfully, you can delete all
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Once your backup has finished successfully, you can delete all
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``<archive-name>.checkpoint`` archives.
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``<archive-name>.checkpoint`` archives.
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How can I backup huge file(s) over a instable connection?
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---------------------------------------------------------
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You can use this "split trick" as a workaround for the in-between-files-only
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checkpoints (see above), huge files and a instable connection to the repository:
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Split the huge file(s) into parts of manageable size (e.g. 100MB) and create
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a temporary archive of them. Borg will create checkpoints now more frequently
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than if you try to backup the files in their original form (e.g. 100GB).
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After that, you can remove the parts again and backup the huge file(s) in
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their original form. This will now work a lot faster as a lot of content chunks
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are already in the repository.
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After you have successfully backed up the huge original file(s), you can remove
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the temporary archive you made from the parts.
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We realize that this is just a better-than-nothing workaround, see :issue:`1198`
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for a potential solution.
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Please note that this workaround only helps you for backup, not for restore.
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If it crashes with a UnicodeError, what can I do?
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If it crashes with a UnicodeError, what can I do?
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-------------------------------------------------
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-------------------------------------------------
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