Copy from one HD to another :)

So i have two HD full of Files, files are ordered by First letter, then inside name of the person that created and inside that the month when i was created..

So There are folders A to Z, inside these folders there are names, and inside these names months.. For example

M -> Miguel x -> December

Like i said i have 2 HD one has the months from January to July and the other one from august to December...

What script can i use to combine these two and keep them on the same order... So it will look at HD A and look for names that are no in HD B and copy them. And if that name exist go inside that folder and copy the names that are missing...

btw im using linux..

Sorry if it is confusing

---------- Post updated at 10:35 AM ---------- Previous update was at 10:31 AM ----------

will rsync do that? since it does incremental copy's?

I don't see why it wouldn't work to simply do a recursive copy (rsync -a will work for that) from one dir tree to another. Normally you'd have to worry about overwriting files, but as I understand it, all path names should be unique, right?