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Comment by james-skemp | Hacker News Reader

Since it comes up so often now, reformat the drive and then do what to verify that it's a legit drive, and not one that advertises as being larger than it actually is?

Put a bunch of large media files on it and verify that they still play properly?

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I always use this tool https://github.com/AltraMayor/f3

It fills the entire device with data and then tries to read it all back. It can tell you how many bytes were successfully read, how many were corrupted and how many were written over by other writes.

Even on cards I know are real I still run the test because I have had a card that had a few bytes that got corrupted which caused loads of issues with my rpi.

I usually use f3probe, which IIRC uses some heuristics and trades of accuracy for speed, i.e. it doesn't write to the entire drive.

The docs are lower down the page from the main f3 utils:

https://fight-flash-fraud.readthedocs.io/en/latest/usage.htm...

The test time can be pretty insane on the high capacity cards. I remember it took about 4 hours to test a 256gb card but I find its worth it to check the card just once since it saves a lot of pain later when you find one tiny part of the card is failing.

I used h2testw on Windows to do this. It writes a 1-GB files with a special pattern on the disk until it is full (or however many GB you specified before starting it). It then tries to read them all back to see if they have been written correctly.

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