We have discussed backups here before, so here is a little history:
https://www.pentaxforums.com/forums/everything-else/14182-dvd-backup.html https://www.pentaxforums.com/forums/pentax-dslr-discussion/11871-transfering-...rd-drivre.html https://www.pentaxforums.com/forums/everything-else/7216-backing-up-images.html
Now on to the current stuff.
RAID disk sets are not backups - they are a method of providing fault tolerance. There is a big caveat - If your disk controller dies, you just might not be able to get your data back. If your motherboard dies - you may not have the proper interface (I just bought a SATA card that is PCI - the mother board is too old to have PCI-X - with two 750GB drives as RAID 1 - mirrored --my two other drives are IDE as are my CD-RW and DVD-RW) The brand new Dell desktop my company bought me does not have a IDE interface on it.
DVD's (my choice of backups - or disaster recovery) my not be viable in the long run also. Just look at the HD DVD vs Blu-Ray - those poor b*stards that bought HD DVD are so SOL. Blu-Ray on a laptop (the current version) will drain you batteries in less than a half a movie and the v2.0 of Blu-Ray is not compatible with the current run of V1.0 readers/writers. Backward compatibility is not a Sony strength.
USB hard drives (my reluctant second choice for some stuff) is just another hard drive. If you read the threads listed above -- you will find out that I have some experience with hard drives and the result is, they will fail, or the interface will just go away. (anyone remember MFM and RLE disk drives? Hint: they were the "standard" before IDE) Even SCSI is giving way to iSCSI and iSAS/iSATA drives on big Data Center servers. As I said before, motherboards are being produced without any IDE interface at all and even PCI slots are starting to disappear.
Digital images are much more sensitive to damage. You need a computer -->> power and software to view them. Film - hold it up to the light and store it in a cool dry place. OS's change/monthly or at least every few years. Software used to read the images changes - just what will happen when your software backup vendor is bought out (Veritas, Legato etc) goes out of business or just plain does not work on new/old hardware? What about the differences in proprietary RAW files (just look at the "I can't read my K20D in Lightroom/CS3/CS2/PSE/PSP/PPB" threads). Things will change and it is up to you to figure out what to do and how comfortable with your workflow.
Should you back things up? - yes. Should you use CD/DVD/USB/TAPE - yes, use something. Should you be ready to copy everything to a new format when it comes out? - yup. Will the follow on generations be able to see your work - maybe - if you printed it using archive paper and ink. Will they be able to read your CD/DVD/USB/TAPE? Probably not, but they will have something to make wall hangings out of.
Maybe I should take my favorites and send them off to the Library of Congress for Copyright registration. The feds know how to keep a lot of c*ap around for a very long time.
The Elitist - formerly known as PDL