HOWTO test SD cards and identify fake ones (mostly sold on ebay)
SD-cards, specially microSD cards, are very popular sine they can store a lot of information on a very small thing which can be read by most devices such as phones, tablets, notebooks and desktop PCs with a $2 card reader.
 Fake SD cards
SD cards are becoming rather cheap, specially the smaller-sized ones, but there is still a price difference between a 8GB card and a 32GB card. This makes it profitable to reprogram a 4 or 8 GB card to say it is a 32 GB card when it in fact is not. These cards are found in both normal stores and webshops and are specially common on e-pray (pray that you get something remotely resembling what you actually ordered).
 How to test a SD card
Simply mount the fat filesystem and run f3write /run/media/you/disk/ and wait hours. Then unmount the filesystem and eject the card and wait 5 minutes before you plug it back in. Now mount the filesystem and run f3read /run/media/you/disk/ and it will test the card.
If the card is fake then f3reads output will look like this:
SECTORS ok/corrupted/changed/overwritten Validating file 0001.fff ... 2097152/ 0/ 0/ 0 Validating file 0002.fff ... 2097152/ 0/ 0/ 0 Validating file 0003.fff ... 2097152/ 0/ 0/ 0 Validating file 0004.fff ... 2097152/ 0/ 0/ 0 Validating file 0005.fff ... 2097152/ 0/ 0/ 0 Validating file 0006.fff ... 2097152/ 0/ 0/ 0 Validating file 0007.fff ... 2097152/ 0/ 0/ 0 Validating file 0008.fff ... 1553440/ 543712/ 0/ 0 Validating file 0009.fff ... 0/ 2097152/ 0/ 0 Validating file 0010.fff ... 0/ 2097152/ 0/ 0 (...)
This is the output of a fake card sold by "FIVE STAR STORE" which operated under the aliasas "sseariver2009", "beautyzz2009" and "victoryduanshop" on e-bay.
You may also want to try https://github.com/flagsoft/sdspeed
 What to do if the card is such fake
If the card turns out to be a fake and the real size is like 8GB then you can use fstab and create a filesystem on it by entering a size such as 15480000S which is slightly lower than the amount of sectors you would find on a normal 8GB SD card. You can use the "actual" size of a "fake" supposedly larger card but you may not want to store important things on it long-term.
 E-Pray sellers who are scammers and sell fake SD cards
- PAYPAL 孔岩 "*KONGYAN" using e-bay user "abigdealstore1"
- PAYPAL "*FIVE STAR STORE" using e-bay user "sseariver2009", "beautyzz2009" and "victoryduanshop"