Cannot unlock screen while backup is busy

I have started a system backup, to USB drive mounted inside a Qube, 800 GB, encrypted and compression, has been running over night. Tried to unlock screen in the morning, but cannot. Disk activity LED on laptop shows busy disk, No login dialog appears. Switching to terminal with ctrl+alt+f3 doesn’t work. What can I do? Last hope is that I wait until backup is complete?

Depending on the hardware, systems can get bogged down by intensive I/O. I’d wait. Meanwhile, some questions:

  • What exact hardware are you using [CPU, RAM, drives (SSD/HDD), USB-Controller/Enclosure]?
  • What version of Qubes are you running? What template versions?
  • Has this happened before? Was the backup the same size?
  • Have you done anything (read: update) that might have changed the state since the last backup?