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List:       rsync
Subject:    Re: Rsync incremental backup solution implemented?
From:       Ben Escoto <bescoto () stanford ! edu>
Date:       2001-06-29 6:30:35
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Ok, I subscribed to the list, so no need to Cc me.  Thanks to Andrew
and Ian for the helpful replies I have already received.

    I suppose since there is no premade solution, I should outline
what I had in mind.  It doesn't have much to do with tape
necessarily.  Suppose the problem is to backup one hard disk to
another.  I would like what's on the other hard disk to have one of
two forms:

1.  (For local backups) Target HD ends up being mirror of source HD,
    but target HD also has reverse deltas on them.  If I delete a file
    or something on the main hard drive, I simply copy it from the
    target hard drive.  However, if I realize I deleted or improperly
    changed a file two weeks ago, I can use the current version of the
    file along with all the deltas to recover the old version.

    The main benefit of this is that it would be really easy to
    understand if the files are getting backed up properly, and if one
    HD failed, the other one could be used in minutes (booting from
    floppy and specifying a different root filesystem might restore
    the whole system).

2.  (For remote backups) Target HD contains a large encrypted file of
    some sort.  Signature information is stored locally.  Each
    incremental backup sends over just an encrypted delta without
    reading what is on the target hard drive.

    This seems like it would be a good system to use if the remote HD
    isn't secure, since not much about the original data can be
    inferred from what is on the target HD.  Increments would be
    pretty cheap, but restoring might require that everything get sent
    over from the target HD.

So does this seem like a good system?  Is there some reason not to do
things this way?

If it is an ok way to do things, what would be the best way of going
about doing it?  For (1), rsync+ almost seems to do what I want, but I
am having some issues with it.  (2) may be more important, but I'm not
sure how it could be done.  librsync?  Thanks for any advice.


--
Ben Escoto

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