The DAM Book by Peter Krogh has some valuable insight on this and other topics related to managing photos.
My personal setup (since we're sharing
):
a. PC with RAID 1 config (mirrored). This results in two physical copies of each file.
b. External drive enclosure attached via USB3 and two drives rotated in the enclosure periodically. This ensures one backup copy is always disconnected from the PC.
c. Files are managed in "Albums" on the drives. When a given album reaches ~22GB, it is burned to Blu-ray and a new album is started.
d. Files are copied from main drive to archive on external drive after each editing evolution.
e. I use
Carbonite for off-site storage. It backs up my entire photo folder hierarchy to the cloud on a continuous basis.
I use Lightroom for photo ingestion and have it configured to copy each file to a backup location on the external drive. For each file, this provides 3 logical copies (original media, external drive, internal drive) and 4 physical copies (2 on RAID array, 1 on external drive, 1 on original memory media) after ingestion. I frequently delay re-formatting memory media until after final editing of photos, but never before at least an initial scan of the photos to ensure they have been ingested correctly by Lightroom. Lightroom is also configured to backup its catalog to the external drive.
Once Lightroom is configured, these copies are created automatically. Moving albums or sub-folders from the PC to the external drive is a manual step after edits for a given set of photos is complete.
While I do not make a living as a photographer, I have had to explain to my wife how we lost 4 years' worth of photos and videos of the family. (See earlier reference to failed power supply.)
The arrangement above greatly mitigates my risk of repeating that discussion.