How Long Do Flash Drives Last?

Will You Outlive Your Flash Drive?

A flash drive contains a circuit board populated with transistors; usually one transistor per bit of storage capacity, although newer (and more expensive) transistors can store multiple bits. To store data on a flash drive, an electrical current changes the charge of a transistor from one state to another, representing either a zero or one, on or off bit. The design of the transistor is such that it remains in a given electrical charge state for many years. So your data stored on a flash drive won't fade away in any time frame that you're likely to worry about.

Flash drives are not as easily damaged as magnetic or optical media. There are no delicate moving parts in a flash drive such as read/write heads, spindle bearings, or disks of magnetic or optical media spinning at thousands of RPMs to collide, strike dust particles, etc. Yes, a cheaply made keychain USB flash drive's case may break if dropped or otherwise abused, and that may be the end of the flash drive's usefulness. But a digital camera's memory card is a flash drive, too, and it is so well armored and sealed you can drive a car over it or drop it in water and it will still work.

Can You Wear Out a Flash Drive?

If you just write data to a flash drive, unplug it from the computer and put it in a drawer, its memory will probably last longer than yours. The age of a flash drive isn't what's important. It turns out the crucial factor in flash drive longevity is how many times data is written to a particular storage block.

There is a limit to the number of times a flash drive's transistors can be switched from one electrical state to another; eventually, it will become impossible to write data to an exhausted transistor. In one hands-on test, this limit was found to be over 90 million write operations! Interestingly, the data already on the tested flash drive could still be read even when writing new data to it was no longer possible. Data was not lost.

I wouldn't consider that the final answer to the question of how long a flash drive will last. I've seen other people quoting an upper limit of 1 million write cycles per block, and cautioning that data loss could happen after 10 years of storage. Given that they're a pretty cheap form of storage, I'd personally err on the side of caution and move my data to a newer device every few years.

Flash Drive Quality

Flash drives can be purchased at dirt-cheap prices online. But you should take care that you get what you pay for. Look for a drive with a warranty of at least one year, as this is some indication of how much faith the manufacturer has in their own product. Some popular and well-respected brands are Sandisk, Kingston and Lexar.

Defective flash drives discarded by manufacturers are often scavenged and sold cheaply. Such a drive may be labeled as a 64 GB capacity, and your computer may even identify it as that size. But in fact, all but a handful of the bytes on the defective flash drive may be unusable. Fortunately, there is a free, easy way to determine the true capacity of any flash drive.

H2testw is a free, tiny utility that writes test data to a directory on your flash drive, reads it back, and verifies that what was written is what is read back. It's safe to use H2testw on a flash drive that already has data on it; no existing data will be overwritten or altered. But those untouched parts of the flash drive may contain defective transistors, so it's a good idea to run H2testw on an empty drive, after quick-formatting the drive. The site is in German but the "download" buttons are in plain English. Just click the first one, then the one on the next page, and your download should start. You can select English or German during the program's startup.

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