Digital photos are very fragile. Ask anyone who has had a hard drive crash. That kind of data loss is sudden and can be tragic. But it can be prevented if you have a good backup routine. Remember the cardinal rule: Data must be in at least two places and one of them must be off-site. Best practice is to have one local backup and one remote backup which could be a cloud service or another external drive that you keep at your aunt’s house.
The other kind of data loss that is more insidious is data corruption. It sometimes happens when you’re shooting but usually it’s later on, when the images are transferred and stored. If it happens in the camera or on your memory card you’ll see it right away as you’re shooting. If your photos ever have stripes or odd color bands while shooting, put another memory card in the camera. If the errors are still there you know it’s the camera. If they’re gone you know it was that other card.
Once the images are on your main hard drive is where the trouble can pop up. A digital image is made up of millions of “words” of digital information. If just one letter of one word gets switched or corrupted in some way it can destroy a photo. The more damage there is, the worst the visual effect is. This kind of damage is not reversible. What’s especially concerning is that you won’t usually notice the errors until you open up an image for years ago. Somewhere along the way the file was corrupted but you won’t know till you view it. That corrupt file has most likely been backup up so all copies will be damaged.
This kind of data corruption comes from three major sources. The first is an actual mechanical hard drive failure. The second is an electronic or connection issue. Disconnecting a hard drive while it is writing data will frequently result in corruption so be careful with your external drives and do not ever bump, drop or move a hard drive quickly. If you’re using a solid state external drive, or SSD, you’re in better shape since they are very resistant to physical trauma. The third, and most mysterious source of data corruption, is what’s called bit rot. This is the random corruption of those bits and bytes (the words) and it can happen at any time. This is a good overview of the problem. https://getprostorage.com/blog/bit-rot-stop-destroying-your-data/
There are a couple of ways to prevent bit rot. One is to buy a RAID storage system that does data scrubbing or parity checking. That just means that the device regularly looks through all the files and repairs them based on some fancy software. The other option is to convert all of your files to DNG format if you use Lightroom. DNG uniquely has data correction built in and you can, at any time, have Lightroom go through and check all the files through its validation routine. It can’t fix the corrupt files but at least you have time to replace them from a backup.
Having a favorite photo show up with green and pink stripes or grainy blocks is heartbreaking. Following some precautions will minimize that risk. One final way to prevent corruption? Print your favorite images or make a book! Neither of those crash or have to be loaded into a computer to enjoy.