abw at wardley.org
Fri Jan 15 20:16:09 GMT 2010
On 14/01/2010 17:41, Philip Newton wrote:
> Yes - you're missing the fact that in order to compute the differences
> (which it has to if it doesn't want to transfer the whole file), it
> has to read the entire file over the slow NFS link into your
> computer's memory in order to compare it with the "local" file in
> order to tell which pieces have changed.
No, I don't think it does.
My understanding[*] is that it computes a checksum for each block of a file
and only transmits blocks that have different checksums. That's how it
handles incremental changes on large files (e.g. an extra few lines at
the end of a log file doesn't require the whole file to be transmitted).
Some relevant options are:
--checksum always checksum
--block-size checksum block size
--whole-file transmit the whole file
--size-only compare file size instead of checksum
[*] which could be flawed
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