Cannot Erase Storage Card

PaulSG wrote:

Ok I get that (I think); but, (and excuse my ignorance) if I were to re-format the card would that not delete the content which I am trying to access?

From earlier:

Another storage card - apparently empty but when Disk Utility opened shows 2.6Gb used (see pics). So am desirous of finding our what is on the card but cannot see what or where!

Seemed rather less like a request to access data from that comment, and rather more like a report of FAT being problematic.

If this is about accessing data (potentially) still on that SD card, and if Finder shows nothing, then you can either seek out and employ FAT file recovery tools (e.g. Disk Drill), or you can use Disk Utility to reformat (erase) the volume and ready it for re-use, depending on how much time and focus (and potentially how much money) you want to expend with investigating the contents of that SD card.

If you want to know more about FAT itself, here are copies of Microsoft FAT specifications, and these can provide some background on the organization and setup, if you’re very curious about that:

https://academy.cba.mit.edu/classes/networking_communications/SD/FAT.pdf

https://www.cs.fsu.edu/~cop4610t/assignments/project3/spec/fatspec.pdf

These specs or similar would be the basis for creating a FAT file system tool, or creating FAT file recovery tools.

The bit about FAT32 really being FAT28 mentioned earlier is from page 16 of the latter document: “Note how the FAT32 code above works. A FAT32 FAT entry is actually only a 28-bit entry.”

Is the write-lock slide switch on the SD card locked, if your card has such a lock?

If you’re using this among Macs, reformat and use HFS+ or APFS, and not FAT.

As for FAT, that is poorly designed and flaky, with differing block sizes which lead to differing addressing limits, too.

I don’t recall the details of the FAT addressing limits offhand, but do recall discovering FAT32 was really rather closer to FAT28 as it was implemented.

Long with legal encumbrances from Microsoft too, encumbrances that lead to many differing interpretations, and with no reference standard or tests, and which in aggregate led to bugs. If it glitches, reformat it. If it glitches in one particular device, use that same device to reformat it. Or better, rework the data transfer process to eliminate use of FAT, or of sneakernet.

Microsoft relented and published some FAT specs in 2019, but diverging and incompatible FAT implementations will exist for the foreseeable future.

Some general background: https://en.wikipedia.org/wiki/File_Allocation_Table

TL;DR: erase and reformat as FAT and test again, or reformat as HFS+ or APFS if solely used with Apple gear, or eliminate its use entirely is feasible.

PaulSG wrote:

Re: MrHoffman 7:10PM

Is your answer in relation to my second question? If so I don’t understand how that might help me discover content of storage card. Could you clarify

That was a reply, yes.

FAT is a problematic design. (I’m being very polite here.)

It wasn’t a good design to start with, and Microsoft only made things worse with their legal efforts.

Don’t use FAT. Find other ways to transfer the data. Other storage formats including HFS+ or APFS, or use wires or wireless transfers, or SMB shares. Whatever.

If you must use FAT, reformat it on any error or oddity. If FAT-related errors are arising only on one device, reformat there.

PaulSG wrote:

Oh dear - seems I’ve confused the issue.

All I want to do is, if possible, discover what 2.6Gb worth of used up space actually contains - it most likely being something that I wished to keep given the fact that it was stored on the card originally.

With the Finder in focus, press Shift + Command + Period/Dot keys (press all 3 keys at the same time).

This will toggle showing hidden files On & Off within the Finder.

Another option would be to connect that SD Card to a Windows PC to see if you have better luck accessing its contents.

Someone already suggested this option earlier in this thread. Unfortunately Apple has the default sort order of posts on this forum to be Ranked which ends up placing posts in random order making it very confusing & impossible to see new posts. You can change the thread's sort order to "Oldest" so that each post appears in an easy to understand linear timeline. The sort order option is just below the gray horizontal line just after the original post.....or if a post is marked "Top Ranked", then just after/below that post on the right you will see "Sort By" with a dropdown list box with other options.

Or you can change the default "Sort By" ordering for all threads by making this change within your Apple Discussions settings which can be accessed by clicking on your avatar at the top right & selecting "Preferences".

You surely will have already tried First Aid on that card too.

Yet, have you thought about trying to use zsh (Terminal) to see if it can find anything on the card? I'd figure that'd be an option which might give additional results?

xWauwau wrote:

You surely will have already tried First Aid on that card too.

Yet, have you thought about trying to use zsh (Terminal) to see if it can find anything on the card? I'd figure that'd be an option which might give additional results?

Worth a try, but I seriously doubt Finder and the command line will show any differences here, as both are accessing the same FAT file system data.

Command-Shift-Period displays hidden files in Finder (as does ls -ale@ or other such ls command at the command line), but I would not expect those hidden or leading-dot files on any FAT volume from a camera. I’d expect both to be the same, and this just FAT being FAT.

A recovery tool might find something.

Well, most likely MrHoffman is right, just figured we'd give it a go.

I don't really feel well recommending any specific recovery tool though as I personally have never gotten to use any, so I don't have any experience with that… maybe MrHoffman has a suggestion there.

Sure… that is our goal as well. It's just that if, let's say, the file paths are corrupted, a professional recovery tool as mentioned might be able to rebuild the index better than Apple's disk first aid. Or something like that.

PaulSG wrote:

Apologies if I’ve been unclear; my aim is to just discover what, apparently, is still on this particular disc before I erase it.

If you Finder’d it and found nothing shown, erase and reformat it, and enjoy the rest of the day…

If you’re concerned there might be something still on the SD card, erase it selecting (if available) the Disk Utility erasure security options to overwrite. (An erasure option which might not be available here.)

Then if you’re very concerned there might still be something in the SD card, destroy the card.