Rsync for backups - possible major speedup when local files renamed.

[jw schultz]

On Wed, Oct 08, 2003 at 11:44:01PM +0800, Will Smith wrote:
> I use rsync regularly for backups of large trees, sometimes
> over low bandwidth links, and I would like to suggest a potentially
> major speedup under some circumstances, where files or
> folders are moved or renamed.
> 
> The principle is simple : often people rename a file, or move
> it from one folder to another.  Current behaviour (please correct
> me if I am wrong) is for wget to see this as a 'delete' and
> an 'add'.  The 'add' results in a complete retransfer of the file.
> This could be optimized.
> 
> For example, if I move local file 'huge_file' to 'old/huge_file',
> a complete retransfer happens to the remote end of the
> 'new' file.
> 
> 
> My proposed implementation is that out the outset, during generation
> of file lists of local and remote, the checksums of entire files
> be computed (already happening with --checksum, I believe).
> Then the local and remote files are sorted by checksum and
> compared.  If two files (one local, one remote) have the same
> checksums but have a different filename/path on the remote
> end, the remote end simply moves and renames the file
> (creating folders etc as appropriate).
> 
> Would this work?  Has it been covered before? 


This has been covered many times.  Read the archives.

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	J.W. Schultz            Pegasystems Technologies
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