This is more on the subject of photography but would also apply to scans of one’s art, such as Urban Sketches.
I’ll be on my soapbox now. It never ceases to amaze me. I talk with people who take photos and learn they don’t back them up. Some even leave them on their phone or on the SD card. In my opinion, neither is a good idea.
Throughout the year, I maintain a folder of my year’s photos and a backup on an external hard drive. At the end of each year, I also make 2 copies on DVD’s. One of those is stored away from home, at my husband’s office.
Digital photography gives us the option of more than one copy. It is absolutely essential to have backups. At least one should be on a drive other than one’s main computer. It is also optimal to have backups on 2 different kinds of media, such as a hard drive and a DVD. For those who keep significant amounts of Cloud storage, that could also be a location. I do NOT recommend keeping the only back up on a photo hosting service. My main one just changed its policy this year and no longer maintains the full resolution “original”. You can never be sure their data is secure or backed up. I remember one service that lost all its customers’ data a couple years ago.
The DVD backup project for 2012 resulted in 9 discs! That’s the most ever. The backup for 2011 was only 3 DVD’s. This is also my first full year of retirement, so it would seem I’ve been out photographing a lot. Each day is in its own folder and there are 3 copies of each photo: the unedited version, the edited version and a copy for the web which is lower resolution (usually 640×480). The total is about 40 gigs! My 2012 Urban Sketches are 1.5 gigs themselves.