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more details about checkpoints, add split trick, fixes #1171

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Thomas Waldmann 2016-06-24 22:32:38 +02:00
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commit f54f159db8
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docs/faq.rst
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@ -180,13 +180,53 @@ Yes, |project_name| supports resuming backups.
During a backup a special checkpoint archive named ``<archive-name>.checkpoint``
is saved every checkpoint interval (the default value for this is 5
minutes) containing all the data backed-up until that point. This means
that at most <checkpoint interval> worth of data needs to be retransmitted
if a backup needs to be restarted.
minutes) containing all the data backed-up until that point.
Checkpoints only happen between files (so they don't help for interruptions
happening while a very large file is being processed).
This checkpoint archive is a valid archive (all files in it are valid and complete),
but it is only a partial backup (not all files that you wanted to backup are
contained in it). Having it in the repo until a successful, full backup is
completed is useful because it references all the transmitted chunks up
to the checkpoint. This means that in case of an interruption, you only need to
retransfer the data since the last checkpoint.
If a backup was interrupted, you do not need to do any special considerations,
just invoke ``borg create`` as you always do. You may use the same archive name
as in previous attempt or a different one (e.g. if you always include the current
datetime), it does not matter.
|project_name| always does full single-pass backups, so it will start again
from the beginning - but it will be much faster, because some of the data was
already stored into the repo (and is still referenced by the checkpoint
archive), so it does not need to get transmitted and stored again.
Once your backup has finished successfully, you can delete all
``<archive-name>.checkpoint`` archives.
How can I backup huge file(s) over a instable connection?
---------------------------------------------------------
You can use this "split trick" as a workaround for the in-between-files-only
checkpoints (see above), huge files and a instable connection to the repository:
Split the huge file(s) into parts of manageable size (e.g. 100MB) and create
a temporary archive of them. Borg will create checkpoints now more frequently
than if you try to backup the files in their original form (e.g. 100GB).
After that, you can remove the parts again and backup the huge file(s) in
their original form. This will now work a lot faster as a lot of content chunks
are already in the repository.
After you have successfully backed up the huge original file(s), you can remove
the temporary archive you made from the parts.
We realize that this is just a better-than-nothing workaround, see :issue:`1198`
for a potential solution.
Please note that this workaround only helps you for backup, not for restore.
If it crashes with a UnicodeError, what can I do?
-------------------------------------------------