Q: What type of flash media has the best long-term storage reliability?

I'm aware that all flash media has varied limits on lifetime write cycles, and that there are better media for long term storage, such as archive-quality optical, tape, and long term cloud storage. But I'm specifically looking for something that could be kept on my person or in a desk drawer or even a fireproof safe, for instance, and which can store small amounts of data, which can be added to very occasionally over time, and is portable and easy to access in an emergency.

Use Case / Background:
This is for emergency/critical personal info that is sensitive, but needs to be accessed quickly -- ranging from financial access info to security keys for cloud storage, for instance. I've just had far too many USB drives and SD cards suddenly become corrupt because they sat in a drawer for a year or two and presumably just wore out from age; this is precisely what I'd like to avoid (or minimize the chance of, at least).

I'm not looking for brand/product recommendations (that would be out of scope for SU) but for specific types or technologies that are known to be more reliable and stable (of course, if one brand has a unique technology that works well for this case, that would be relevant). I can use your answers to do my own product research. ;)


By far the most common backup media employed by people is the external hard drive. Fast compared to tape and optical, hard drives are generally reliable for the short term, and if removed from operation and safely stored, may last a decade or two before magnetic properties diminish to the point of producing unrecoverable errors. In constant use, mechanical stresses shorten a drive’s lifespan to three to five years. For the long term, hard drives on the shelf are workable, but require periodic maintenance—so they are not ideal.

That decade or two longevity figure is based on published figures for coercivity and residual magnetism for current GMR (Giant MagnetoResistance) and SMR (Shingled MagnetoResistance) recording techniques, as well as the latest platter coatings. It figures a loss of magnetic strength/signal at anywhere from 1 percent per year, to 1 percent per decade.

For non-operational drives, it’s industry practice to refresh, i.e., rewrite the data every two or three years. You can do this with free software called DiskFresh.

Environment is also key: Heat, vibration, humidity, and magnetic fields (strong ones are used to erase hard drives) can dramatically shorten operational or shelf life. A hard drive is also a mechanical device that’s vulnerable to shocks. You can do everything right with your drive, but drop it on a hard floor as you pull it out of the safety deposit box, and like that, you’re off to the recovery service.

Advice: If you use hard drives for archiving, use them in pairs or trios—each containing a copy of the same data. Write-protect them before storing them, and rewrite the data every couple of years.

  • 1
    This is decent advice for a general backup strategy. However, I am really interested in information specifically about flash (solid state) media, especially as used in smaller-capacity, portable devices such as USB "thumb" drives & SD cards. – Brian Lacy May 22 '18 at 20:01

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