Identifying counterfeit microSD cards on a Beaglebone Black

[Dr. Rolf Jansen]

I bought a 16 GB microSDHC SanDisk chip rated at 4 MB/s write speed for use with my Beaglebone Black. 

The internal flash offers practical write speeds in the range of 2 to 3 MB/s when copying data to it from a NFSv4 volume depending on the size of the files being copied. Executing the same copy operation with said microSDHC card as the target I see only 0.1 to 0.2 MB/s (less than 1/10).

I suspect now that I got a counterfeited card. Before I dump it, I would like to run a definitive non-destructive test, preferably on the Beaglebone Black, and I would like to ask you for suggestions.

Also, it would be nice to see some speed values as a reference for microSDHC card write speeds on:

    FreeBSD 12.0-CURRENT (BEAGLEBONE) #0 r315413

Many thanks in advance for any help.

Best regards

Rolf