Re: How to resume an scp transfer?

From: Darren Dunham (ddunham_at_redwood.taos.com)
Date: 04/29/04

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    Date: Thu, 29 Apr 2004 18:08:00 GMT
    
    

    Jack Moe <mojorisin@bigmailbox.net> wrote:
    > Kyler Laird <Kyler@news.Lairds.org> wrote in message news:<hhh2m1-fbo.ln1@snout.lairds.org>...
    >> mojorisin@bigmailbox.net (Jack Moe) writes:
    >>
    >> >That's interesting. Didn't think of that. 'rsync' supports delta
    >> >transfers, too.
    >>
    >> Be careful with them. The original (partial) transfer is not just extended
    >> when the transfer is resumed. A new file is created. Thus, if you are
    >> moving a 10GB file and you get 9GB before stopping, then resume, you'll use
    >> up to 19GB until the transfer is complete.
    >>
    >> (At least that's the way it worked awhile ago when I investigated.)
    >>
    >> --kyler

    > What version did you test this with.

    > Per rsync's web site at http://rsync.samba.org/features.html
    > "rsync is a file transfer program for Unix systems. rsync uses the
    > "rsync algorithm" which provides a very fast method for bringing
    > remote files into sync. It does this by sending just the differences
    > in the files across the link, without requiring that both sets of
    > files are present at one of the ends of the link beforehand."

    The two statements above are not incompatible. My understanding is that
    while only the differences are sent, they do not modify the existing
    file. To avoid problems of disconnects in the middle of a transfer,
    rsync needs to complete the transfer to a separate file, then move the
    file into place. If a problem occurs in the middle of a transfer, the
    temp file can be safely deleted.

    I'm not sure how it works, but that could easily be done by making a
    (local) copy of the existing file, then running the rsync algorithm to
    apply differences.

    -- 
    Darren Dunham                                           ddunham@taos.com
    Senior Technical Consultant         TAOS            http://www.taos.com/
    Got some Dr Pepper?                           San Francisco, CA bay area
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