Out-of-universe, it's probably just a mechanical/electronic piece of set dressing that, as you say, is meant to resemble a vintage hard drive or a "future" version of the same, because it's unlikely that a genuine computer drive would be affordable or conveniently available for use as a prop. Likewise, the console in the background simply has some fairly basic electronics installed for effect but is a completely self-contained prop unit.
Prop consoles from UFO were apparently reused by other television productions of the time, including Doctor Who, and it wasn't unusual for prophouses to make all sorts of electronic or mechanical set dressings that looked like complex pieces of futuristic hardware but in fact did little more than light up or have some minor mechanical function like the spinning disks in the prop you've shown. These props were owned by the prophouse and were rented out to productions that needed them, sometimes in identical or modified form depending on production needs.
Here's an article about that: https://www.gerryanderson.co.uk/five-shows-that-reused-ufo-computer-props/