Disk Test program for testing fake flash drives
Compilation results in two programs: dfill and dtest.
dfill fills a device with 64-bit incrementing numbers. dtest reads those numbers and checks they are right.
The idea behind this program is to fill a flash disk with numbers. Starting at 0 and counting up the numbers are written to the raw disk as 64-bit values. The first 8 bytes of the device should therefore be
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
The second 8 bytes should be (little endian):
0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x00
And so on up to the end of the disk.
The testing program then performs the same counting through the disk, but instead of writing to the disk it reads the numbers from the disk and compares them with what they should be. As soon as a number is found that is wrong the test program terminates reporting where the error was, what the expected number was, and what number was actually read.
First you need to fill a disk with numbers. Caution should be used to ensure you get the right device name, since
it's possible to completely distroy your Linux installation if you get the wrong device. In this example the
flash drive is detected as /dev/sde - use dmesg when you insert the drive to find out the device name you should use.
The command must be run as root, so using sudo is a good idea:
$ sudo ./dfill /dev/sde
Once that has finished (it will take some time, and it does a basic verify test as it runs) you can test the data:
$ sudo ./dtest /dev/sde
You can expect, if the drive is fake, for it to fail with output similar to:
Read 7727 MiB
Read error at 8103247872 (1016755668 != 1012905984)
That was taken from a fake 32GB drive. It appears to only have about 8GB of real flash in it, and everything above that gets squashed into the last few meg of the flash.