Use a different format for sd-card as portable storage (ext3, ext4, extfat)

Just found this thread:

which points on this one → ✏ List of compatible micro SD / SDXC cards for FP4

I have a 128GB SanDisk Extreme A2. Maybe it is also such a SanDisk SD related problem.

For the record, FP4 here, latest updates. I got me a Kingston Canvas Go! Plus SDCG3 of 256 GB, which came factory-formatted as exFAT. The phone did accept it (“portable” setting) and the default camera didn’t have any problem using it to store pictures.


Also, for the record, SD cards have a somewhat special formatting and should if possible not be formatted with the usual (Windows/Linux/Apple) tools. You risk problems on the long run.

Fortunately the SD Association offers a free SD card formatting tool (Windows and MacOS only).

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Got a Samsung PRO Plus 256GB U3 A2 V30 Class 10 and it arrived exFAT factory-formated as well. The FP4 with CalyxOS accepts it without any issue as portable storage.

I will not go on researching this, as I shared a lot of details here (with my former FP2 [which the thread is also tagged with] → FP4 now) - and I was out of ideas, but I’m still curious what this “special” should be. At the end exFAT is exFAT, the formatting tools cannot do it differently. There has to be something in the header or so, which makes it special. Also there could be device differences and or newer Android Versions handle all this differently.

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I had problems with my Sandisk 512 GB U1 card with exFat so I ordered a SAMSUNG EVO Plus 512 GB which works fine even after formatting it under Linux.
I wanted to try ext4 first. BTW I do not understand why this is not working for many Android versions and different devices, now. Except for AOSP or LineageOS based systems.

Well, it’s just an educated guess, but I think it has to do with “overprovisioning”, i.e. the fact that flash memory-based disks (SD cards, SSDs) keep a stash of unused memory cells to use when (it’s not “if”, it’s “when”…) one or more memory cells cease to function. Think of it as spares.

I assume the “special” formatting is all about preparing the disk for this, so the firmware can do this without the user even noticing. And that’s the obvious explanation, there might be something else too (write amplification prevention, wear leveling, TRIM, etc.). There are lots of special functions a flash memory based disk requires to be able to work optimally, so I guess exFAT on a SD card is actually just something posing as exFAT to the OS: “Don’t worry, I’m just an exFAT disk, I’m not some monster from out of space”… :grin:

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