H2testw allows you to test storage devices for various errors.
It is particularly useful for detecting fake USB memory sticks and microSD cards, (Writing speed around 2mb/s & Show defective)
where it attempts to detect the actual capacity versus the reported capacity of the memory.

Note: H2testw wipes out all the content on the target device during testing!
Be sure to backup the content on the device before running H2testw.

H2testw software download: http://www.download3k.com/Install-H2testw.html

Beware of fake microSD card.

If memory is defective or fake, You will encounter the following problems:

1. Corrupted data.
2. Frequent need to reformat.
3. Difficulties with saving files.
4. Extremely sluggish performance, especially with large files