Reed's First Law: On Long-term Data Storage

The Law

If you want to keep information for a long time, never separate the head from the recording.


This law is based on a lot of experience with generations of data storage devices with removable media (punched cards, tape, magnetic disks, CDs, LPs, ...). Long before the information decays on the medium loses the information, people manage to lose the ability to access the information because the access mechanisms become obsolete extremely rapidly. For example, I backed up a fair number of useful files from my days at MIT on 9-track tape, using a Multics tape format. Now, of course, I can hardly find means to read them ...

So the law says something fundamental about using removable media to archive long-term storage - since you can't depend on the world to keep producing the devices needed to read your media, you have to keep a reader (head) with your archive.


If you don't want to pay the cost of keeping and maintaining the heads, you must keep moving the data bits to contemporary media.