Correct way to disconnect/eject an USB hard disk ?

[RW]

On Thu, 20 Aug 2020 04:43:52 +0200
Polytropon wrote:

> The USB controller accepts and confirms the last
> chunk of data, reports back "Got it, everything is fine."
> Now the umount command does what it says on the can, it
> unmounts the medium, and returns control to the user.
> Now _internally_ the USB stick is still busy _actually_
> writing the last chunk of data to its storage, ...
 
> The idea of "just give it a few seconds after you physically
> remove the USB stick" relies on the assumption that such
> kind of activity takes place outside the control of the OS,
> and the OS has no real way of discovering what's really
> happening at that point.

I'm wondering how "now safe to remove" notifications work in windows
and other operating systems. And is shutting down or suspending to
disk just guesswork?

I don't know, but I'd be surprised if there aren't mechanisms  in sata,
usb etc, to ensure data has been committed to non-volatile storage.