can rsync scan files only with mtime since T?

[Matt McCutchen]

On 8/23/07, Ming Zhang <blackmagic02881 at gmail.com> wrote:
> I have a file system that contains millions of small files. Since I
> backup it everyday with rsync using slow WAN link, I think it will be
> nice that if rsync can do this:
>
> An option that let rsync only check with remote rsync daemon about local
> files that has last modification time newer than one day ago (so is
> modified since yesterday backup). This can greatly reduce the WAN
> traffic.
>
> Is this doable with current rsync?

No.  A request for enhancement has been entered for a --newer option
that would do this: https://bugzilla.samba.org/show_bug.cgi?id=2423 .
At present, I can think of two things you might try:

1. Use `find' to list the files that need to be checked and pass the
list to rsync using --files-from, as described in the request for
enhancement.

2. Use Unison ( http://www.cis.upenn.edu/~bcpierce/unison/ ) instead
of rsync.  If I understand correctly, since Unison stores the state at
the last synchronization on both sides, the local Unison knows which
files have changed since then and mentions only those files to the
other side.  (Someone please correct me if I am wrong about this.)

Matt