Backup vs sync: why Google Photos is not a backup

Most people use the words interchangeably. The distinction only matters once, but when it matters it matters completely.

Sync keeps two places identical. Change something here, it changes there. Delete something here, it disappears there.

Backup keeps a separate copy that is deliberately protected from what happens to the original. Delete the original and the copy survives.

The behaviour that defines a backup is not the copying. It is the not deleting.

Where this bites

Google Photos, iCloud Photos, OneDrive and Dropbox are all primarily sync services. Their default behaviour is to mirror. If you delete a photo on your phone while it is synced, it goes to the trash in the cloud too, and after a retention window — commonly around 30 to 60 days — it is gone.

That is correct behaviour for a sync service. It is exactly wrong for the scenario people actually fear:

• You clear space on your phone by mass-deleting old photos, not realising that clears them from the cloud too.
• An app or a bug wipes a folder, and the deletion faithfully replicates.
• Ransomware or corruption alters your files, and the altered versions sync over the good ones.
• You delete something and only notice eight months later — past the retention window.

In every one of those, sync propagates the damage. A backup would not have.

The rule worth knowing

The widely used standard is 3-2-1: three copies of your data, on two different kinds of storage, with one copy off-site.

Your phone is copy one. A cloud account is copy two and satisfies the off-site requirement. A computer, external drive or NAS at home is copy three. Most people have one copy and a sync service, and believe they have two.

Where one-way sync sits

Between the two extremes there is a useful middle: copy in one direction only, and never delete at the destination.

This is how iFileSync works, and it is a deliberate choice. Files move from your Android phone to your iCloud Drive. New and changed files go up. Deleting a file on your phone does not remove the copy in iCloud.

The practical consequence: clearing space on your phone is safe. The cloud copy stays. That is backup behaviour, not sync behaviour.

Being honest about what it is not

One-way copying is not a complete backup system, and it would be dishonest to present it as one:

• No version history. If a file is modified and re-uploaded, the new version replaces the old one at the destination. You cannot roll back to last Tuesday's copy.
• It is one destination. It satisfies the off-site copy in 3-2-1, not the whole rule.
• It is file-level, not device-level. Your Android apps, settings and SMS are not included. Google's own device backup covers that, and the two work side by side.

A quick way to tell which one you have

Ask one question of any service you rely on:

If I delete this file on my phone right now, is the copy in the cloud still there in six months?

If the answer is no, or "only for 30 days", it is sync. That may be perfectly fine for what you use it for — but do not count it as your backup.

A workable setup for most people

1. Sync for convenience. Google Photos or similar, so your library is on every device.
2. One-way copy for safety. An additive copy into a second provider's account, so a deletion on one side cannot reach the other.
3. An occasional local copy. Drag your camera folder onto an external drive twice a year.

Using two different providers matters more than it sounds. It protects you from account-level problems — a lockout, a billing failure, a mistaken policy strike — which are far more common than a cloud provider losing your data.