External drives · Upgrading, transferring and backing up the drive
What happens if I cancel Transfer Drive or Backup Drive part-way?
Short answer: Cancelling removes the half-finished copy from the new drive only. Your current drive is never touched by Transfer or Backup, so nothing you have is affected. Use Pause if you just want to stop for a while.
Cancelling removes the half-finished copy from the new drive and leaves your current drive exactly as it was. Transfer and Backup only ever add data to the new drive; nothing on your current drive is touched at any stage, so cancelling can't harm what you already have.
If you only want a breather, use Pause instead and resume later.