file1 is on the NAS mounted ServerA.
user@ServerA> scp /mntnas/file1 user@ServerB:/dest
will the file1 transfer go through ServerA or directly from NAS to ServerB?
You are logged in as
ServerA, therefore scp will start an ssh session from
ServerB to copy the file.
scp doesnt know anything about networked storage it will let the filesystem handle giving it the bytes that the file is made up of, so your file will be transferred from
NAS -> ServerA -(ssh tunnel)-> ServerB