This is what h2testw was invented for: It tests the real size with a method explained later on, and compares it to what the drive says. What does this mean? Whatever your unix tools tell you about the capacity of the drive: It's what the tools asked the drive, nothing more. If the controller is programmed that way, it can just ignore the command or overwrite something with the data. It also decides what is done, when it receives the command to store something. This means that the client device needs it's own controller with some knowledge about the devices purpose and, in this case, it's capacity. Serial Interfaces have the common property, that the client device (the usb drive) will need to tell its own capacity via this serial interface. You do not need to know the USB-Protocol well to unterstand the problem. Send more data than it can really hold, you'll get a data loss. This is fatal, since your OS regulates how much data you can send it to. The capacity of usb devices your operating system or unix tools give you, can be wrong. So I try to explain it as short as I can in details, though I think this is much to the extend of my question. It seems that some people do not understand the problem. "Clearly figure out what is the problem you're trying to solve and what is the definition of "fake drive"." What is the problem and why does dd alone not solve it? I did not read all of them in detail, due to missing time.ĭue to the strange critics below, some explanations. I tried to get together some sources in English. I'm actually searching for an application like those, but for Ubuntu/Linux:
Unfortunately I can only find a few information about this on English tech sites. I want to test if all data I write will be readable again. It's not like I want to see if I get 128 GB instead of 127.3 GB. Update: Just to be clear, the idea is to verify that the size the linux system gets told by the controller is correct ( so no data will be lost). Is there an easy way to test this on Ubuntu/Linux? A specialized, well working tool maybe? I read that for Windows, H2testw does the trick. But I hoped there is a more accurate solution. I could also automate it with Hashes and stuff.
I could just copy stuff on it, copy it back and look if the files are okay.
It's not bought via ebay or something, but I really want to test the real size before using it productively. I recently bought a SanDisk USB drive (128 GB claimed) and want to test its size.
I recently read a lot about fake MicroSD card and USB thumb drives that claim to have a lot of space (even if you ask your computer), while physically offering way less.
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