I would steer clear of USB sticks for large backups unless you want lots of USB sticks as they will get expensive. Flash memory has a limited number of writes. This isn't to say it will fail after 3 writes or some other small number, but the lifetime gets shorter with smaller cells and denser capacities. Mechanical drives also wear out but a good quality hard drive will typically last a long time. I would say base your decision on how much you want to store
USB flash drives use the same memory that is used in SD cards and have similar controllers. This means that their wear leveling isn't as good as what is in SSDs. Hence you should formatting them every now and then o that they can move the file allocation table sectors which is what will see the most wear. SSDs will do this automatically which is why it isn't an issue with them.
If cost is a concern a single 4TB external hard drive of reasonable quality can be had
for under a hundred bucks. A 256GB flash drive of reasonable known quality
can be had from about $25. So to get the same storage capacity with flash drives it would cost you about 4x more. If you don't need 4TB of storage a 1TB external drive of known reasonable quality
can be had for about $50.
This isn't to say that USB flash drives aren't a viable solution but they really need more redundancy than just one copy. I use them for backing up important documents and have a few 32GB ones. In my use of them I use several of them. One is in my pocket, one is in my car, one is in my desk drawer at work, and one is in the fire chest at home. There is also an electronic copy of the documents on my computer at home and any paper documents the originals are in the fire chest. Now this is a lot of redundancy in a lot of places but these are actual important documents. For backing up images I wouldn't say you need that level of redundancy, unless you are a pro photographer where having the images means eating while not means starving, so having the originals on the computer, and 2 external drives would probably be more than enough.
Once I replace my existing computer here in a couple of months the existing one will be converted into a NAS which will add in another layer of redundancy provided that I don't do a RAID 0 configuration. For important things like those documents I will probably still keep them on USB sticks as well but they will live on the NAS. My images will eventually live on the NAS but I will probably go down to just one external hard drive for a backup.
Originally posted by Racer X 69 I have a 3 drive RAID array built with three 2 TB hard drives. If one should fail, the other two have identical copies of all my images.
With a 3 drive setup RAID 1 seems like a waste when RAID 5 would get you expanded capacity and resiliency against a single drive failure.