What is being checked in a smart update?

[astrodog]

Odd question I know...

I was making a backup of a large media drive, decided to do the grunt work manually in stages by copying the bulk over manually using Finder drag/drop, then a smart-update to tidy-up.

Problem was that SD! didn't recognize the data I've copied as identical in some way... and insists on recopying everything, all 900GB of it!
Is this normal, or have I set something incorrectly?

Needless to say I'm just using SD! to do the grunt work now, but am interested to know how this all works.....

Happy New Year too.... :)

[dnanian]

Pretty normal. We're checking the file dates, times, size, attributes, premissions, EAs, metadata, etc. Finder doesn't preserve all that with a normal Finder copy.

[astrodog]

Thanks.... Lesson learnt! Poor little USB drives have never worked so hard.....