The card is full, the next setup is waiting, and the camera op wants it back. The question is simple and unforgiving: is it safe to format yet?
The rule everyone quotes
The 3-2-1 rule is the working standard: three copies of the footage, on two kinds of media, with one offsite. It is the target for the whole job, not a thing you finish on set.
On the shoot itself, the part that decides the wipe is smaller and concrete: two verified copies, on two separate drives, before any card goes back in the camera.
Why two, and why separate
A drive can fail at any moment, with no warning. With one copy, that failure loses the footage. With two copies on two separate drives, one failing leaves you whole. That is the entire reason for the second copy.
The word separate matters. Two folders on the same disk are not two copies. If that disk dies, both folders die with it. Real redundancy means two independent drives.
One drive failing should never be one job lost.
Verified, not just copied
Two copies only count if both are checked. A copy that was never read back could already be corrupt, which leaves you with one good copy and a false sense of two. The safe state is two copies that have each been read off their disk and confirmed against the card.
The short version: aim for 3-2-1 over the life of the job. Before you wipe a card, the bar is two verified copies on two separate drives. Stow holds the verdict at amber until you reach it.
Sources
- Massive.io, The 3-2-1 backup rule
- Frame.io, Checksums and backups for media workflows
Stow enforces the two-copy bar
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