Thursday, February 3

512GB microSD for $6 – Too Good to Be True

What you see above is the output of a flash card testing tool called f3read. File 15.h2w is where the corruption sets in…

Let’s step back. About a month ago a friend of mine enthusiastically told me how he ordered a super cheap 512GB microSD card for his camera. Just a few dollars, no shipping cost. From China. Of course I was more than skeptical, having fallen prey to at least a couple of cases of fake flash cards before.

But for the sake of the greater good, I went ahead and bought not one, but two cards. One with 512MB and the other with 256GB (allegedly).

Together they set me back a whopping $10.
Let me tell you how it went.

Here’s How They Do It

Let’s first look at fake cards and how they come to be.

I’m vastly simplifying here, but in general this is what happens when manufacturers make new flash cards: They don’t make separate cards for 16GB, 32GB, 64GB, 128GB and so on. Instead it is much cheaper to produce mostly larger cards, test them for speed and bad blocks and remap the cards to their final size. So if you buy a 32GB card, it probably mean that the memory chip inside of it is bigger, but it has bad blocks beyond 32GB. The meta-information on the card makes sure that your camera will never get anywhere close to the faulty memory blocks.

This is perfectly normal. Until the fraudsters come into the picture. Some people just have too much criminal energy.

The (original) factory will scrap memory cards that don’t adhere to a minimum quality level, or they sell them cheaply, because they are either too slow or have too many bad blocks. What the fraudsters will now do is mess with the meta data on the card. The information that tells your camera or computer how many Gigabytes the card can hold.

By manipulating that information on the card, just within a few seconds, they turn a 16GB card into a 256GB card. Bad blocks and all.

I Tried It, so You Don’t Have To

Hey, what’s not to like about the prospect of getting a fast 512GB microSD card for only $4. Yes, four US dollars. So I went ahead and ordered two cards, one that said Huawei Pro Plus, 256GB, UHS Class 3 (30MB/s), and the other with the same stamped-on specs, but 512GB in size. It took about 4 weeks for them to arrive, as I opted for free shipping from China.

$10 for two cards: Huawei Pro Plus UHS Class 3 256GB and 512GB. Including SD adapters and a USB microSD card reader each.

When the cards arrived the other day, I ran f3write against them.

f3 – The Tool

f3 is a suite of command-line tools. I run them on my Mac to test each and every new flash card that I get. Here’s the f3 website. If you use homebrew, the install is as simple as typing

brew install f3

in the terminal. There’s a Windows alternative too*

Here’s how you do it: You’ll need to be a bit comfortable using a terminal and the command line, but it’s not too hard.

First format the card (I used ExtFat as the filesystem), then run

f3write /Volumes/NAME_OF_YOURCARD

The tool will write sequencial 1GB files to the card until it is full. Yes, with 500GB it writes 500 individual files. That will take a while. Several hours in my case.

Writing 500 1GB files onto a slow(ish) memory card takes time…
… and then reports an average writing speed of 20.81MB/s

After successfully (allegedly) writing all 512GB, the average write speed is reported as 20MB/s, which is below the UHS Class 3 promise of 30MB/s, but hey, the card was only $6, so who am I to complain?

I used a reasonably fast card reader to do the test.**

Reading It Back

After f3write has filled the card, all you have to do is run f3read against it. Same syntax, different command:

f3read /Volumes/NAME_OF_YOURCARD

then lean back and wait. Mine ran over night, but I could have stopped it much earlier.

f3read tries to read back all the individual 1GB files, to determine these three things:

  1. Find out if they can be read at all
  2. Find out if they are the same files that have been written
  3. Find out how fast the card can be read

In case of the 512GB card, the corrupt sectors started showing in file 15.h2w, which translates to: This 512GB microSD card has 14 usable Gigabytes on it.


I didn’t expect it to be quite as bad, but you get what you pay for.

Oh Look, a Free Card Reader

Just for kicks and giggles, I did the same test using the USB card reader that came in the box. The write speed instantly caved to about 11MB/s, which is a bit over half of what the faster card reader did.

Another Reason for Corruption

Not all corrupted cards are fake cards of course. Another way to introduce file systems issues is to pull a memory card before the camera has stopped writing to it. While unlikely, it’s definitely possible.

I’m convinced that the 2-second-rule*** has saved my butt (aka the photos on my memory cards) more than once.

Learned Something?

So I knew what I was in for when I ordered the cards and $10 aren’t too much to spend for a good story on a blog and a podcast. But your reasons for buying a card will probably be different ones.

So what can we learn something from this?

  1. Buying something as easy to fake as memory cards from non-reputable sources is probably a bad idea. The least I will do is make sure I can return the card if it turns out to be a dud.
  2. Religiously test all cards the moment you receive them. Even the ones you bought in a store. Worst case is you return them. But at least you’ll know their write and read speeds.
  3. Stick with brands you know and that haven’t let you down in the past. Of course ownership can change (as we saw with Lexar), but at least so far this hasn’t failed me. I won’t give you a specific brand recommendation, but I stick with a big name that has been around a long time.

And of course: If it’s too good to be true, it probably is.

Was It Worth It?

Was it worth for me to buy the two corrupted cards? Absolutely! From the perspective of someone who creates podcasts on photography, this makes for great content while helping some others to avoid the same issue.

I also learned that things are still as bad as they used to be 10 years ago.

How about financially? Even if I managed to “repair” the metadata on the card and turn it into a proper working card that officially reported 14GB as its size (it’s possible), it wouldn’t really work out: At the time of writing this article, I can get a perfectly good 16GB UHS Class 10 microSD card for well under $10. I paid $6 for a dodgy 14GB card that claims to do 512GB and that took 4 weeks to arrive. And for which I don’t have any hope of returning it and getting my money back.

At least they tossed free microSD USB readers in the box albeit slow and flimsy ones.

But for the majority of readers I’d say keep your hands off those cheap offers. Spend a few more bucks to get something decent. You can buy a 128GB UHS Class 3 microSD card from a reputable brand for well under $30.

Above all, is it worth the risk of losing valuable photos? Probably not.

* The Windows alternative is called H2testw from German publisher Heise.

** I used my pretty descent USB 3.0 Transcend TS-RDF8K card reader to do thes tests.

*** The 2-second rule: After turning off your camera or after opening the card latch, wait for two seconds until you physically pull out the card. Some cameras will write to a card for a second after you turned it off and pulling the card too early could lead to corrupted data. I haven’t had a flash card issue in 10 years.