Preservation
“I have a backup drive” isn’t enough
Most photographers keep a copy of their images on an external drive. It’s better than nothing, but it leaves the two most common causes of data loss wide open: the single physical incident (the drive and its copy sit in the same drawer, exposed to the same theft, fire, or flood) and propagated error (a deleted or corrupted file quietly copies itself onto the backup).
The 3-2-1 backup rule exists precisely to close these blind spots. It fits in one line: three copies, on two types of media, with one kept off-site.
Three copies
Three copies doesn’t mean three identical drives, it means your working original plus two independent backups. The logic is probabilistic. Any single medium has a non-zero chance of failing; two failing at the exact same moment is already rare; three is improbable. Each additional copy sharply lowers the risk of total loss.
Two types of media
Two types of media, not two units of the same one. Two SSDs from the same batch, bought the same day, share the same manufacturing flaw and wear pattern. Mixing technologies (an SSD and a spinning disk, a NAS and object storage) prevents a single common weakness from taking out every copy at once.
One copy off-site
This is the most overlooked point, and the most decisive. An off-site copy lives somewhere other than your originals: another building, or remote storage such as Amazon S3, Backblaze B2, Cloudflare R2, or a NAS at a friend’s place. It’s your only protection against a local disaster. Without it, “three copies” in one room is still a single target.
Backup, sync, and archiving are not the same
Three different actions that are often mistaken for one another:
- Sync mirrors a folder to another in real time. Convenient, but dangerous as your only safety net: a deletion or corruption propagates instantly.
- Backup keeps dated copies that let you roll back. It protects against time and mistakes.
- Archiving sets aside a fixed, documented, verifiable set for the long term, one you no longer modify.
Sync alone is not a backup. And an active backup is not yet an archive.
A concrete example
A freelance photographer returns from a shoot. The RAW files are on her Mac (copy 1). That evening, they’re copied to an external drive (copy 2, a different medium). Once the project is culled, a documented package is pushed to remote object storage (copy 3, off-site). If the Mac is stolen, the work still exists twice; if a file corrupts locally, the fixed remote copy stays intact.
In practice
- Count your real copies: a mirror sync doesn’t count as two.
- Confirm that two types of media are involved.
- Make sure at least one copy is physically elsewhere.
- Separate what’s in progress (backup) from what’s fixed (archive).
Obscura Flow guides that off-site copy to S3, Backblaze B2, Cloudflare R2, a NAS, or a local folder, with resumable uploads. The goal isn’t to pile up drives, it’s to make the 3-2-1 rule genuinely sustainable in daily practice.