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I'm trying to make a back-up of my Windows machine to an external usb-connected SSD. However, when I click "Add a drive" in "Backup Settings" I'm informed that "No usable drives found". Additionally, no drive is found via Control Panel\System and Security\File History\Select Drive.
I can see and access the drive in File Explorer, so I don't think it's a problem with the drive. The drive is formatted with NTFS, but is slightly smaller than the drive it's backing up. However, the data it's backing up is smaller than it's maximum capacity, so I would be surprised if that's the problem.
What are the requirements for a hard-drive to be used as a backup in Windows 10?