Longevity largely depends on choosing the right medium. The majority of old data has been preserved till nowadays on paper copies. It is surprising because paper catches fire easily, can be damaged by floods, and chewed by rats. The main secret is that, usually, there were many copies of same book or manuscript. Many of them perished in time but some of them survived, because they had been kept in archives, libraries or private collections.
Based on described examples, there are two factors which determine longevity of any data: the number of copies made of original data, and how widely they have been distributed between different locations. For example, printing a book in 50,000 copies gives a very solid ground for saving it for 100 years. Having many copies of texts published in Internet may or may not be sufficient for preserving it with the same success. Internet sites usually require more resources than having a paper book somewhere. Our culture has, also, a deep respect towards books, and no electronic medium has yet achieved such status. Any Internet server takes energy, hardware needs replacing and software requires maintenance. The tradition of keeping texts in Internet is new and we can not really be certain that our files will last for 100 years on the net.
There seems nothing wrong with keeping your important data in the same way it has been done for centuries, i.e. in printed form. Some file formats, like .txt, .rtf and .doc, will probably have a pretty long life, too. The most burning question is where should we save those files to still have them available after 100 years.
Make many copies and distribute them
Having important data just in one computer is a certain recipe for disaster. Hard drives are the most vulnerable parts of any computer and they will most certainly not survive more than 10 years (which is about 10 times shorter period than we need). Distributing copies between different computers helps a bunch: if one hard drive crashes, data is still available in other locatons.
The problem with keeping data in computers is that they wear and tear, and need to be replaced after a certain period of time. Programs become more massive and need new operation systems as well as more powerful hardware.
One solution to this is to use an online storage provider, who takes care of the maintenance of servers and software necessary for keeping your precious files safe. It is certainly a convenient way to make automatic backups and keep them in another location. It means that you do not need to worry about hard drive crashes, fire, flooding, theft or any other local disaster. Online data storage services are pretty new. They are definitely worth looking at as one element of your data backup plan. Yet, the longer future of online storage providers is unknown, and you should also look for other options on your own, in order to keep your data safe.
One day I was cleaning up my drawers and found 15-year old CD-R disk with my old articles on it. I took a look at the content of this CD and discovered my old works, which were perfectly stored and in very good condition. I have been doing backups in various forms but using CDs seems to be one of the easiest and cheapest ways to store data safely. In my recent article "Are CDs and DVDs Still Good for Data Storage?" I compare CDs and DVDs, and came to a conclusion that they both are still very good mediums today.
We all would like to have our data safely saved for a long time. Today, it is hard to name any other mediums that are universally useful and probably also readable after 100 years beside CDs. Recently I made a really cool discovery: I found a CD brand called "Archival Gold for 300 years". I tried these disks out and found them pretty solid for archiving my important data. It is well known that gold resists oxidation, and, apparently, that extra layer protects also against scratches, scuffs, dirt, chemicals and fingerprints.
Easy recipe to keep data for 100 years
Save your data in multiple formats onto the medium which is the most probably readable in the future. Use only the best quality disks, which are designed for lasting long. Make multiple copies and keep them all in different places (at home, fiend's house, office and rented vault).