People use all the above and more, some use 64GB USB Keys even. For myself I put everything on an external hard drive, and use a same size drive to back that up should something happen to wipe out that archive of work.
You will probably never see it as common sense or worth the investment, until you lose the hard drive - it usually costs a lot more to recover it, if it's possible at all. In instances where the platter has to be removed (fire usually) you'd be looking at over £1000. I can rescue on a limited number of issues for less than half that. Makes far more sense to spend £80 on a 2nd backup drive. If you can afford it, you might even want to use a large cloud service.
I back up every shoot to a DVD. I also save them to my computer HDD, and to a separate computer HDD in a different building. I also save them to an external HDD. Finally, they go on iCloud too. I should also say that some edited images are saved on various internet sites, such as Dropbox temporarily, and Flickr too.
DVDs of RAW files immediately after shoot (I don't even look at the images)
Don't wipe memory cards until you're 100% confident all backups are made and are successful
Everything stored on a mirrored NAS which is backed up to two separate external drives
Finished shoots (fully edited) are then also backed up to DVD / BluRay
Golden rules for backups:
- keep multiple copies, preferably on various media (which can also include different hard drives) in case the media may be part of a bad batch
- do so regularly
- refresh old backups from time to time (CDs, DVDs, BR and hard drives can all fail over time)
- preferably keep copies in multiple locations
- always use checks on copies (ie. CRC checks) to ensure the backups have worked
- have a good, clear strategy for how to go about this, backup/synchronisation software can help with copying files (copying only what's needed and verifying through CRC checks)
- never trust flash media as it can wipe itself over time, and I personally don't trust tapes (in all the years/companies I've worked at, tapes have never worked successfully)
Two ext hard drives, 2TB each. One is labelled Master or Primary the other is Slave/Secondary. All work saved to Master then to Slave. Like AndyG mentioned, you tend not to realise the importance of a good backup system until you lose data. I'm also quite paranoid about handling drives carefully, no knocks or sudden impacts. Also, from experience, always disconnect USB device correctly. Cheers
1TB Buffalo RAID5 Terastation NAS backing up to a 2nd identical unit and then backed up again via my network to a 2TB RAID 5 Terastation in another part of the house which itself backs up to a 2TB USB drive. Belts and braces!
I was forced to stop using DVDs when I bought my first 5D (6+ years ago) as the RAW files from big shoots meant I was using far too many discs. Since that time ext HDDs seems to be the best option still. I'm a bit nervous about how much data would be lost if a 2TB drive became corrupted, but I make sure to always double back up and touch wood, no problems so far
Son, Father, Grandfather. Camera to laptop, deleted from camera, laptop for working then before I do anything with the images I download the files to an external hard drive, then ever week I download the original files and any files I've worked on to a second external hard drive which is then stored in a separate room to the original external hard drive. Not like in the "old days" when you had prints and negatives or reversals and prints