I ask this because recently Rufus has been reporting most USB drives as having 256 errors. Brands that I would not expect to have high error rates: SanDisk, Lexar, etc. Or are the expected shortages really that bad such that good USB drives are that rare in common consumer channels?

I was thinking maybe there is now on some USB drives an addressable area for Manufacturer and serial numbers that might being misread as writable areas of generic flash - but which is actually read only.

Yeah I realize brands can be counterfeited especially from Chinese sources. And of course Chinese counterfeits can travel supply chains and show up in any place or reseller in the world. Especially since counterfeits are sometimes manufactured by or shipped from the same Chinese plant that makes the legitimate products.

In previous years it would have been a bit odd statistically to get counterfeit batches from 3 sources and in 3 different major brands. Plus problems with various promotional drives received from else where.

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    Well, if they're read-only, what happens when you try to read them? Do you find any data that looks like a serial number? – grawity Jan 4 '18 at 8:13

Rufus developer here.

Nope, there is nothing in Rufus that will produce false positives during the bad blocks check. If Rufus says a block is bad, it means either that:

  • A read or write error occurred while accessing the block.
  • The data read from the block does not match the data that was written to it.

Now, if you are getting a seemingly high rate of defective drives from different sources, and you are testing them on the same computer, it might simply be that your USB connection is defective. This can be especially true if you are using USB 3.0 drives with an extension cable, as subpar USB 3.0 cables are prone to adding interferences.

At any rate, if you have doubts about the results provided by Rufus with regards to bad blocks check, I'd encourage you to try a different verification utility, to confirm that you get the same outcome.

By the way, 256 is the number of errors when Rufus gives up with bad blocks validation (too many defects), which is why you will see most problematic drives reporting 256 errors, because the verification process simply didn't continue after reaching that many errors.

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