64B Ultra card seems to be read-only

I have a 64GB Ultra MicroSD card which has been working fine in my phone for a year or so.

Recently the phone has been acting a little strange, and I’ve tracked it down the the MicroSD card - it seems to be unable to hold on to anything I write to it.

I can save a file to the card, and read the file perfectly well while the card is still mounted. If I unmount the card and remount it, the file is gone. The same with deletions, and even formatting. I can do a full NTFS format (not a quick format) and the card appears blank, and I can save new data to it, and read it. If unmount the card though, it’s back to the state before the format - I can read all the files on it too.

The only thing I can think of is that the file allocation system is corrupted somehow.

Really strange. Have I just managed to get the card into a read-only format, or is it broken?

Also, I’m not using an SD-card adapter. I have it in my phone and have the phone connected via USB in data-transfer mode.

And yes, I meant ‘read only’ in the title… :flushed:

Most memory cards come formatted as FAT32. The newer, larger capacity 64GB cards are formatted as exFAT. The fact that you have re-formatted it as NTFS may have something to do with your problem.

Thanks. I’ll try reformatting it tomorrow. This happened before the reformat though, the format was just an extreme example of it ‘forgetting’ what had been written to it.

Nope. Reformatted it as exFAT and the same thing happens. It sits formatting for about an hour, before a 'Format complete; message pops up. If I open it in Windows Explorer, it shows up as blank, with 59GB free, exactly as you’d expect.

I can read and write to/from this, save files there, view them, copy them back, everything you’d expect.

However as soon as I unplug the card and reconnect it, it’s back *exactly* as it was before the format, showing all the files it held previously.