Which of your files are not backed up anywhere?

If you have been using external drives for a few years, your files are probably backed up very unevenly. Some projects exist on three drives because you copied them "just in case". Others exist on exactly one drive, and you would not know which until that drive stops spinning.

Why this is hard to see

Duplicates are easy to notice because they waste space you can see. A file that exists in only one place wastes nothing, so nothing points you at it. It just sits there, one failed drive away from gone.

Time Machine helps, but only for what it covers. By default it backs up your Mac, not your external drives, and most people with a pile of externals are not running a separate backup for each one. Photo and video archives in particular tend to live on drives that were never part of any backup at all.

You do not need to back up everything twice. You need to know what you have backed up zero times.

The manual way

You can answer the question by hand, but it is slow. Make a listing of every drive, match files that are the same across drives, and whatever is left is the risky part. Matching by name is not enough, because the same file is often renamed on one drive and two different files often share a name like IMG_0001.JPG. Matching properly means comparing the contents of the files, which is exactly the kind of work a computer should be doing, not you.

Safekeeping in GetFerret

GetFerret already keeps a catalog of every drive you own, including the ones that are unplugged, so it can answer this directly. Its Safekeeping view is the flip side of its duplicate finder: instead of showing files that exist too many times, it shows every file that exists in only one place, at risk if that drive dies.

• It matches by content, so a renamed copy still counts as a copy and two different files with the same name are not mistaken for one.
• One button gathers every at-risk file across all your drives and copies them to a single safety drive, in the background, while you keep working.
• It suggests which drive to use for that copy, by free space and health.
• Files leave the at-risk list only when the copies are really there. After copying, GetFerret catalogs the safety drive again, so the list reflects what actually landed.

And when you do clear out duplicates, GetFerret sends them to Recently Deleted rather than straight to gone, so you can put a file back exactly where it was, even on a network drive with no Trash.

A habit worth having

• Check what exists in only one place after any big project wraps, before the drive goes in a drawer.
• Keep the safety copy on a different drive from the original, ideally one that lives somewhere else.
• Write down where each drive is stored. GetFerret asks you when you unplug a drive, which makes this painless.

The short version

Your riskiest files are the ones you only have once, and nothing on a Mac shows you which ones they are. A catalog of every drive, matched by content, turns that into a list you can fix in one go.