Data wrangling checklist: 3-2-1 backup and checksums

By James Jones, founder of Granary Digital · Updated 5 November 2026

What the checklist is for

It is the list a data wrangler or the camera assistant works through at the end of each setup, before the card goes back in the bag. It covers the offload, the check, the backup and the log. The offload log is the record that shows which card went where, and it is what the post team trusts when the picture is missing a shot.

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Before the card leaves the camera

1. Label the card with the camera letter, the card number and the date.
2. Note the last take on the card and the last clip number in the camera report.
3. Make sure the card is not still being written to. Stop recording before you remove it.

Offload and copy

1. Copy to two destinations at the same time if the setup allows it, not one after the other.
2. Copy the whole folder structure the camera wrote, not only the video files. Sidecar files, audio and metadata are part of the shoot.
3. Keep the source card untouched until the checks below are complete.

Verify

1. Generate a checksum for every file on the source card. A checksum is a short code worked out from the contents of a file. If two files produce the same code, their contents match.
2. Generate the same checksums for each copy and compare them with the source. Any mismatch means that copy is bad, so make it again.
3. Open a sample of clips in a media information tool and check the frame size, frame rate, codec and timecode against the camera report.

Store to 3-2-1

1. Three copies in total: the card, or the first drive, and at least two backups.
2. Two different types of storage. Mix an internal drive with a removable one, or add cloud storage. Drives of the same model bought together can fail together.
3. One copy in a separate place from the others, so a fire, theft or flood at the set does not take every copy.
4. Check the backups again after a day or two. A backup that has never been checked may not restore when you need it.

Only after step 8 is complete should the card be formatted.

Common mistakes

• Trusting the "copy complete" message and formatting the card straight away.
• Copying only to a laptop, which is then the only copy of the day's work.
• Formatting a card that was copied to one drive, with the second copy still to be made.
• Naming files the same way on every card, so the offload log cannot tell two cameras apart.
• Buying three drives of the same model and calling it a backup.

Where it fits

Storage numbers for the shoot come from the data rate and storage calculator. The settings that produce the files come from frame rates and the 180 degree shutter. The general guidance here applies to most shoots, and the data lead on the production sets the actual procedure, including how often the backups are checked and where the offsite copy is kept.

Sources

• Production Expert, Back up basics: the 3-2-1 backup rule, read 5 November 2026

Related guides

• Free tools: MediaInfo, Shutter Encoder, QCTools and HandBrake
• Offload log template for camera cards
• All guides and tools