How to offload an SD card to multiple drives at once on Mac
You just wrapped a card. Before you format it, one question matters more than any other: did every frame actually make it to your drives, intact? Dragging files in the Finder can’t answer that. Here’s how DITs offload a card to multiple drives on a Mac so they can format it with confidence.
Why the Finder isn’t enough
A Finder copy tells you the bytes were written. It never reads them back to confirm they match the source. A flipped bit, a flaky reader, a cable knocked mid-copy — the file looks fine and isn’t. On set, that difference is someone’s only take. This is the entire reason offload software exists.
The rule: 3-2-1, starting on the card
The principle post-production lives by applies from the moment the card comes out of the camera: at least two copies, on two different physical drives, before the card is wiped. A master and a shuttle. One of them ideally leaves with a different person or vehicle.
Step by step
- Mount the card read-only if your reader allows it. The source is sacred; nothing should be able to write to it.
- Copy to every destination at once. Read the card a single time and stream it to a master and a shuttle simultaneously — two physical drives, not two folders on one disk.
- Verify by reading back. After the write, the tool re-reads each copy off the disk (with the OS cache bypassed) and compares its checksum — xxHash, MD5, SHA-256 or C4 — to the source. “Copied” is not “verified.”
- Write an ASC MHL next to the files, so anyone downstream can re-verify without your software. What ASC MHL is.
- Keep a report — the clip list, checksums and destinations, as the PDF or CSV you hand to production.
- Only then format — and only once every file is verified on two physical drives.
Doing it with Olycen
Olycen copies a card to as many drives as you want at once, verifies every file by reading it back with the cache bypassed, writes ASC MHL v2, and shows two numbers — copied and verified — so you never mistake one for the other. It offers the card for formatting only when the proof is in, and it protects the card from being ejected while it is still being read. See how it works or join the beta.
What “safe to format” really means
Not “the copy finished.” It means every file verified on at least two physical drives, with a manifest you can re-check later. Anything less is a hope, not a backup — and hope is not a workflow when you’re holding the only copy.
Keep reading: Olycen vs OffShoot, ShotPut Pro and Silverstack · What ASC MHL is, and why your offload should write it
Offload that never lies to you.
Olycen copies every card to as many drives as you want, verifies each file by reading it back, and only says the word verified once the proof is in. One-time $129, two Macs, no subscription — the launch list pays $99.