Testing a fake 128GB Samsung EVO+ micro SD card

For about $45 you can buy a Samsung 128GB Micro SD card from Amazon. Sellers on Ebay offer them new for a lot less. I selected one for $26, shipped (from S. California), suspect it would be a fake, but curious what I would get. What I got looked reasonably real (shown here after opening).

My phone and laptop both reported full 128GB of space. Interestingly, the case contained the regular disclaimer that 1GB = 1000,000,000 bytes, but presumably in an attempt to avoid suspicion the card reported a full 128GB of space (using 1024^3 = 1GB). I tested it by copying some files to it and immediately had problems. The transfer rate was abysmal, between 1 and 2 MB/s, nothing close to the advertised rate on the package. And Windows kept on saying the card wasn't inserted, or needed to be checked for errors. After checking for errors some of the files were missing. I figured maybe the first part of the disk was bad, corrupting the FAT file system data, so I partitioned the disk in two, starting with a dummy 8mb partition.

The dummy partition helped. The write speed of the disk went up to about 5MB/s and Windows stopped reporting damage to the file system.

I also got more systematic and used a tool called H2testw to verify the actual storage space on the card. h2testw is not the nicest tool, but it got the job done, revealing that a full 24gb of "usable" space on the disk. Well, sort of usable: even keeping within that fraction of space, some of the data written was corrupted, though well below 1%.  So the card had about 20% of the advertised 128gb, which is a pretty bad deal for $26, especially given the random corruption of that 24gb (undetected until read back). For comparison, Amazon currently sells real 32GB Samsung cards for $16, or 50 cents/GB, whereas this card cost about 100 cents/GB.

I suppose I could use it to store my MP3 collection for playing back on a old phone. Time will tell if the usable storage remains usable long enough to make even that worthwhile.

Final note: that SD card adapter was so cheap that it failed after just a couple insertion/removal cycles. See the crack in the lower left corner. Thus, all my tests were conducted with a genuine Samsung adapter.