>Another thing to consider - if both source and destination are the same NAS, is there a "native" copy API you could or should be using instead of Windows file system calls?

This is something we would try to avoid. I am not aware of such utility.

>To show what I mean I'll refer to Novell NetWare file servers of about 25 years ago. If you were copying a file from one server folder to another, you had 2 choices:
>
>1. DOS/Windows Copy command. This caused 2 file transfers:
>
>Source server folder -> across wire to workstation -> across wire back to server destination folder
>
>2. Native NetWare ncopy command. This instructed the server to copy the file from the source to the destination folder, without transferring to the workstation across the network. This could make a huge performance difference with PC/XT workstations and 2.5Mbit/sec ArcNet networking.
>
>If the NAS has a "native" file manipulation API it might be better to use that.

I see.

>That raises a related question: are the NAS volume(s) mounted as SMB/CIFS or something else such as NFS?

SMB/CIFS