Re: Incremental backup including entire file?

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yuraukar wrote:
| My incremental backup created with dar is larger than I expected. The
| reason seems to be, that I have a large file here, which changes a bit
| every day -- this is my mailbox.
| dar includes this file in the incremental backup, but instead of storing
| only a diff to the original one, it stores the entire file. Is there a
| way to improve this?

Not really. If you have a look at diff command, it does not work on
binary files, it works on text file and replace/add/delete a set of line
~ from a file, which is performant if you have only few lines
chaged/added/removed. But in a binary file there is not that notion of
line, so diff is useless (try diff on a executable you will see).

Now what to improve? Making dar detect plain text files from binary
files would consume a lot of time (need to scan the whole file to know
if it is plain text file), if so need to analyse the difference. And
last, need to save the resulting difference or the whole file if it is a
binary file.

At restoration time, restoring the last version of a given file would
become painful, as you should need all the archive from the initial full
backup up to the last differential archive available to restore the file
in the current state. Actually you only need the archive where has been
saved the last revision of the requested file.

What I suggest if you really don't want to save the whole big file that
changes every day is to make a little script that makes the following:
Full backup:
- - make a copy of the mailbox to a special directory
- - save the copy with dar (or the tool of your choice)

Differential backup:
- - make a diff of the current mailbox and the one copied in the special
directory
- - save that diff with dar (or the tool of your choice)
- - replace the copy of your mailbox by the actual mailbox (assuming your
mailbox has not changed since the diff done two steps above).


Cheers,
Denis.
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