Camera card offload guide
How to copy a camera card to two drives on Mac
A second folder is not automatically a second copy. A defensible field-offload workflow keeps the card unchanged, proves that the two destinations are different volumes and verifies every expected file after it lands.
1. Freeze and identify the source
Stop recording to the card, mount it cleanly and choose the exact folder you intend to offload. Inventory regular files before copying, record their relative paths and hashes, and never use the offload step to erase or reorganize the card.
2. Choose genuinely independent destinations
Select two writable locations whose volume identities differ from each other and from the source. Two folders on one SSD share the same failure domain and should not pass as redundant copies.
3. Preflight before writing
Confirm both destinations have enough free space plus a safety reserve. Reject source overlap, unsafe path components, case-folding collisions and existing folders that are not clearly owned by the current offload job.
4. Re-read both copies
Hash the bytes written to destination A and destination B instead of trusting a successful copy call. Keep missing, mismatched and failed files separate per destination, and export a receipt only with the state that actually occurred.
5. Keep the card until the next control point
Two matching local copies reduce one workflow risk, but they do not guarantee the drives will remain healthy. Keep the source card unchanged until your own retention, backup and handoff policy says it is safe to move on.