[rdiff-backup-users] snap-shots every 10 diffs...

[listserv . traffic]

Follow-up on "snap-shots" of diffs.

From this thread ...
http://lists.nongnu.org/archive/html/rdiff-backup-users/2009-01/msg00118.html
I'll quote a bit...

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On Jan 16, 2009, at 7:00 AM, Michael Biebl wrote:

    2.) If one of the rdiffs goes corrupt (e.g. via a bad sector), all my
    older backups are broken.



Every 10 incremental diffs, rdiff-backup stores another snapshot of the file.

So, let's say you have 22 versions of your file. Then, in the rdiff-
backup-data, the two most recent backups would be stored as reverse-
diff increments. Next, there would be a snapshot. Then, nine reverse-
diff increments. Then, another snapshot, then the first nine reverse-
diff increments.    

During the restore, rdiff-backup finds the oldest snapshot at least
as recent as the desired backup time (it could be the current mirror,
or one of these snapshots). Then, it will apply any reverse-diffs
necessary to recreate the desired version.

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So, if I understand this correctly...

The "snapshot" referred to by Andrew is a "snapshot" of all the
rdiffs?

So, rdiff-backup creates a "roll-up" of all the rdiffs every 10
rdiffs. (I'm assuming it's a "roll-up" since there's no facility to
merge the rdiffs.)


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I ask this because this issue of "snap-shots" has caused me and
others some confusion. I think this is especially acute from the
terms used in the discussion. (i.e. snapshot: which I think most of
us would think of as a mirror of the source file at some point in time.)

TIA
-Greg