In the most general terms, the commands run separately.
Certain things on computers are simplified, to make
them easier to understand. This includes novel ideas,
such as copying files directly from one disk controller
to another, without ever leaving a copy in memory. Ideas
like this are generally disallowed on desktops (when this
was brought up in a joking manner to our boss at work
in the hardware design department, he just walked away - that
tells you the idea is just terrible
If he
argued with you, then the idea had merit.)
We could look at more specialized techniques, with
no guarantee that they actually do anything useful for
you. They just meet the need of "winning a bar bet".
Ways to achieve two copies include:
1) Use a RAID 1 mirror setup of two disks. I get two
physical copies, using only one "copy" command.
That doesn't mean the result is "extra useful".
I can only "win a bar bet" doing this.
2) Use automatic synchronizing software, to copy
C:\Downloads changes to your NAS, and from there
to C:\Downloads on your other home computers. As a means
to keep the "view" of files the same on all machines.
This offers no protection against accidental deletion
(as all drives try to comply with the deletion and no
copies are left). But under some circumstances, it would
mean that multiple hard drives have the same file, and
it cost the user "zero brain power" to do it. If one
of the other computers dies, I presume the sync doesn't
go about deleting stuff.
There are softwares with terms like "Time Machine" in their
name, which take most of the pain out of backing up. We had
a wonderful product at work, where you could dial back
the time machine in one hour increments, and find any older
version of file you'd deleted. And it was totally automated.
The IT guy just threw tapes in the autoloader at the end of the
day, and the tapes kept snapshots for future emergencies. It's
the most seamless product I've ever seen, and I don't even
know the name of it
This is what happens when you don't
stick your nose into every install at work
You don't
learn the names. That concept is a little more common now,
than it was when we were using it. We probably paid a fortune
for that package, whatever it was.
HTH,
Paul