rsync - Sep 2018 - Modification times being updated even when time difference is smaller than modify-window

Hi all,

I am using rsync to synchronize across two different filesystems (one is 
an sshfs mount, while the other one is an xfs).

I am synchronizing from the xfs to the sshfs one.

The xfs filesystem has a sub-second resolution for modification 
timestamps, while the sshfs one has a 1-second resolution.

My synchronization are always rather slow. When investigating why, I 
realized that rsync is attempting to set the modification timestamp for 
a bunch of files every single time, even though they have not changed. 
Since I use the --size-only option, it is not transferring files (they 
have not changed), but it is nevertheless attempting to set the 
modification times.

Looking through the manpage, I discovered "--modify-window" which, 
presumably, when set to 1, should avoid this behavior. Unfortunately, it 
does not. I would expect that with "--modify-window=1", it would only 
attempt to update the remote timestamp if the time delta is larger than 
1 second.


Is this a bug or a feature ?

I am using rsync  version 3.1.2  protocol version 31



-- 
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Maxime Boissonneault
Analyste de calcul - Calcul Québec, Université Laval
Président - Comité de coordination du soutien à la recherche de Calcul Québec
Team lead - Research Support National Team, Compute Canada
Instructeur Software Carpentry
Ph. D. en physique