I’ve recently become aware of the risks of buying Micro SD Cards online. I got a new phone a few weeks ago, a Lumia 640 XL, to replace my Lumia 925. As a result, I needed to buy a new Micro SD Card for it. So I went to eBay and did so. I bought one that was supposed to be 128GB, Class 10, SanDisk brand. The card I got looked perfectly normal and brand new.
I put it in my phone. Pictures I took started getting corrupted. I complained about this in a private MVP forum, and another MVP recommended trying a new SD card. I also did some web research to see if there were any tools for testing these cards. There is. One particular tool is called H2TestW. There’s a good article on it at https://sosfakeflash.wordpress.com/2008/09/02/h2testw-14-gold-standard-in-detecting-usb-counterfeit-drives/ and you can download it from SoftPedia at http://www.softpedia.com/publisher/Harald-B-geholz-64417.html . It supports two languages, German and English. What it does is fills the drive with carefully crafted data files and then attempts to read back what it has written. It also reports read and write speeds.
So I formatted the SD card and ran H2TestW on it. The results were alarming. I returned the card and bought a new one, this time a Samsung. I ran H2TestW on it as well. NO GOOD.
The Samsung SD card had lots of data corruption, although it did actually have write speed of 10 Mb/s, which is what a class 10 SD card is supposed to do. So I returned this card too, and went to my local Microsoft store and bought one there. Brand was Kingston. When I got home, I ran the test on it. Sure enough, it was good.
I went and tested the SD card in my wife’s phone, and fortunately it was good.
I went and tested the SD card in my Raspberry Pi, and I notice that Windows is reporting that the 8GB card really only has a capacity of 64MB. Fortunately, that 64 MB has no corruption.
The take away: It’s worth the extra cost to buy microSD cards at a local electronics retailer with a good return policy. Regardless of where you buy it, use a tool like H2TestW to test it as soon as you can!