What is old is new again. IBM mainframes had a concept called a "channel controller". Everything connected to the mainframe basically was a computer itself that offloaded the main system. Every DASD (disk), communication link was its own system.

Random - the Commodore 1541 drive (all of their drives really) had their own 65xx CPU and some RAM (2K IIRC for the 1541). There was copy/backup software where you could hook up 2 devices, load the program and then disconnect the drives from the computer. You could put the master in the first drive, blank disk in the second and every time you swapped the backup it would make a new copy.