--ignore-times broken/redundant?

[Matt McCutchen]

On 2/21/07, Pádraig Brady <P at draigbrady.com> wrote:
> With an rsync-2.6.4-3 client talking
> to an rsync-2.6.8-1.el4.rf server at least,
> the --ignore-times option seems not to be honoured?
>
> I.E. if I edit a file so that the mtime
> and size are the same, the file with the new
> data will not be transfered to the server.
> In case it's important, the full command I run is:
> rsync -viIaz --delete -e ssh . www.pixelbeat.org:'~/public_html'

I cannot explain this.  I tested the option on my computer with plain
rsync 2.6.8 on both sides and it worked.  The sender's version doesn't
matter much because all the sender does is pass the option on to the
receiver.

> Another thing I just noticed is the --checksum option.
> Now I haven't tried this, but what does that do differently?
> If they're equivalent shouldn't they be documented
> together in the man page?

--ignore-times makes rsync transfer the file and rewrite the
destination file no matter what (which has a few side effects even for
unchanged files, e.g., hitting the mtime if --times is off).
--checksum makes each side compute the MD4 checksum of its copy of the
file, and the file is transferred if the checksums differ.  --checksum
increases disk reading in exchange for decreasing network use and disk
writing if some files are unchanged.  (However, if the incremental
transfer algorithm is on, the network use would have been small
anyway.)

Matt