dodged a disaster with my sd memory cards
This could have ended up bad, but thankfully didn't.
I recently spotted a deal on SanDisk ImageMate SD memory cards in 512GB flavor at Walmart, and got two of them.
If you look at the prices 512GB cards are selling for, prices jump around quite a bit even for name brands. Doesn't matter if it's SanDisk, Samsung, Lexar, PNY or something else. That means if you see a deal, you go for it, so that's what I did.
But then I saw this post that someone bought one from Walmart and got screwed. Uh-oh. Now I'm nervous. Did I just get screwed too?
I had to find out.
I'm nerdy enough to know how to blow away and recreate the entire file system on a memory card (or any other media storage), and that is a way to check the actual storage capacity.
Being I hadn't written anything to the cards yet, into GParted I go, and thought okay, let's do this. Blow away the file system. Check. Recreate file system with GPT (no, not the AI, it's GUID Partition Table). Check. Format using exFAT, which is what it had before. Check.
System reports I have the full 512GB available. Good.
Repeat the same for the second card, same result, I got the 512GB. Good.
But even with that confirmed, I needed a file write test just to be sure. And it had to be something over 32GB since that's the limit of FAT32.
While I was certain the 512's I bought were true 512's at this point, if these were 32GB cards masquerading as 512GB, then there's no way a file over 32GB would write successfully.
To the Terminal I go. Time to create a 33GB file, and did so with this:
dd if=/dev/zero of=33GB_file.txt bs=1G count=33
Copied the file over to the first card. It got all sorts of toasty because that's a big file transfer, but the whole file copied and it worked. Good.
Did the same for the second card. Again, worked. Good. Now I'm convinced that my 512's are in fact true 512's. Crisis averted.
Were I still using Windows regularly, I would use HDD LLF Low Level Format Tool to blow away a file system. Yeah, I know DISKPART is there and has been around since WinXP, but past experience has taught me that doesn't always work. Using compmgmt.msc (Computer Management) as an alternative also sometimes screws up. HDD LLF works. I never use that utility to actually format media, but rather because it's the only for-Windows thing I've ever used that when I tell it to blow away a file system on a specific SD/SSD/whatever, it does it without any grief. Once after running that, then I use Windows itself to quick-format an SD card or SSD or whatever. And if Windows still gave me grief after that (such as not assigning a drive letter), I run into compmgmt.msc to get that crap done manually.
It was worth the risk
I went for the two cards because a deal on name brand 512GB microSD is worth the risk, as the price for a 1TB is nuts, and 2TB is insane.
It's like I said, if you see the deal, you go for it, even as risky as that is. I did so, and fortunately ended up getting two legit cards that had their claimed capacity.
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Published 2026 Jan 24