Xcopy: Works fine *to* NAS drive, but not *from* NAS drive

Question

I'm using xcopy in Windows to copy just the changed files between some folders on my local machine and an NAS drive in our office. When I do it from the NAS to local, it works fine (i.e., it only copies over the files that have changed or been added).
But, when I do it from my local drive to the NAS, it always copies over all the files.

Can anyone explain what's going wrong here, and how to fix it?

By the way, here's my call for copying from my local to the NAS (mapped as drive N):

xcopy "C:\cygwin\home\max\work\topics_access_dbs\Topics\Production File System" "N:\Paul's shared\Topics\Production File System" /YIDE

Answer 1

Does your NAS support the archive bit? That's what XCOPY uses to detect changes, I believe. If your NAS resets the archive bit, then XCopy would think all files have changed.