External drives · Upgrading, transferring and backing up the drive
What should I do with my old drive after Transfer Drive finishes?
Short answer: Keep it for a while as a fallback — Transfer Drive never changes it. Once your moved apps and folders work from the new drive and Inspect shows Verified, you can erase or reuse it yourself in Disk Utility.
Keep it until you're confident everything works from the new drive. Transfer Drive never modifies or deletes the old drive, so it remains a complete fallback copy.
Once you've used your Mac for a while with the new drive — opened your moved apps and folders and checked Inspect fast drive shows Verified — you can erase or repurpose the old drive yourself in Disk Utility. Storage Studio won't do it for you. Many people keep it as an extra backup.