cpdup work heads-up

Matthew Dillon dillon at apollo.backplane.com
Fri Apr 11 15:42:26 PDT 2008

:I have used cpdup a few times. Today I read some more in the manpage.
:I see it can do synchronize mirrors remotely. This sounds great.
:Has anyone done any comparisons or benchmarks between it and rsync? I am 
:especially curious if should start using cpdup instead :)

    Well, I doubt it would be faster then rsync.  rsync uses a more
    efficient algorithm that batches better over connections.  cpdup's
    remote algorithm is kinda ad-hoc and uses synchronous transactions
    (-p allows multiple synchronous transactions to be run in parallel).
    cpdup isn't meant to do rsync's job.

    On the otherhand, cpdup is a bit more user-friendly, and cpdup can
    do third party copies (both source and target are remote-host specs).
    It also doesn't try to play naming tricks on the target like cp
    (and rsync) do, e.g.

	cp -r dir1 dir2		(dir2 doesn't exist -> dir2 created)
	cp -r dir1 dir2		(dir2 exists, copies to dir2/dir1)

    Which really screws up a lot of people (and has for over 20 years).
	cpdup dir1 dir2		Make dir2 an exact copy of dir1 (regardless
				of whether dir2 exists or not).

    And cpdup by default, without any options specified, will attempt
    to make as exact a copy as possible whereas with rsync you have to
    tell it to with -a.

    In anycase, cpdup has been around for over 10 years, lots of
    people love it, and I still use it, so I'm going to continue to
    maintain it.

					Matthew Dillon 
					<dillon at backplane.com>

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