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64GB SDXC cards and FAT32 - what's the real story?

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    64GB SDXC cards and FAT32 - what's the real story?

    I was given a Huawei Y6 Elite to replace an LG Optimus L9 which died, not sure if that's relevant, but FYI, the Y6 has "720p" video that looks like it was taken with a 20 year old VHS camcorder....

    Anyway. The Huawei claimed to support up to 64GB cards. I thought this was great, because my old 32GB card was almost full, and so I went out and bought a Strontium Nitro 64GB card. It came formatted to exFAT which after copying all my files to, the phone didn't recognise. I used the phone to format the card. It formatted it to FAT32. I copied all the files again. Everything seemed fine...

    A few months later, I started noticing problems. Some photos I took did not show up in the gallery, although I could read them OK with the file browser. A while later, MP3 playback started skipping, or VLC would just stop playing the file. About the same time, I started getting constant errors about the camera database being broken.

    CHKDSK said the filesystem was bad. I copied all the files off, with the intent of formatting the card and copying everything back. Some files did not copy properly, and were corrupted, but not completely. Some MP3 files for example were 90% OK, but had random bursts of 'digital' static throughout them.

    I was able to copy the important files without corruption - after freezing the card with freezer spray and re-inserting it whenever it started copying files badly.

    I assumed, perhaps incorrectly, that the card's controller was failing. I bought a new card, this time an Apacer R85 (also 64GB microSDXC) and once again, formatted to FAT32, copied all my music etc to it, and started using it.

    It seemed to work great for a while, until one day I tried taking a photo and the phone told me it was using internal storage. I tried to change it back to the SD Card, and found that the card was not even detected any more. Not just bad filesystem, but it acted as if the card wasn't even there!
    Now, the funny thing was, the computer would read it, while the phone wouldn't. I wondered if the phone had gone bad, but found that it could read other cards.


    At that point, I began searching Google for information about 64GB SDXC cards and FAT32. Most posts were about people having problems formatting them due to Windows' insistence on exFAT.
    I did find a few which referenced some 64GB cards claiming that FAT32 was not supported or not recommended due to reliability issues. No card I have ever purchased has said this. The same listings on Amazon for such cards no longer have this disclaimer message, though it certainly seems to have been present at some point, going by screenshots, internet archive etc.
    I wondered if it was just a way for manufacturer's to deny responsibility for corrupt files... but maybe there's truth to it?

    But back to the Apacer card - this one acted a bit differently. When trying to copy files from it, some worked perfectly. Some cause an I/O error, and the card completely drops out and has to be reinserted in the computer's card reader.

    I wondered then, if it was a problem with cheap cards. The Strontium and Apacer cards had both been some of the cheapest 64GB cards I could get at the time. While buying cheap cards seems to have worked perfectly up until now for me with anything 32GB and smaller, I do wonder if a doubling of capacity in such a tiny (microSDXC) form factor could just have made the cheap 64GB cards unreliable, compared to <32GB cards.

    So, I bought a 64GB Samsung Evo+ for twice the price of the other cards. This time, I didn't let the phone format it, though. I put it in my Linux machine, and formatted it myself. I noticed the partition table had a 17MB free space at the start of the disk, and the rest was exFAT. I formatted the exFAT partition to FAT32 with a full format, leaving the free space alone. I wondered if perhaps the card needs this space to operate properly, and if the other two cards had issues because the phone may have removed this free space. Also wondered if the phone's quickformat may have been a problem...

    So we shall see what happens now.

    But in any case, I haven't been able to find a conclusive answer with an official explanation to this apparent "64GB SDXC \ FAT32" question\issue anywhere... does anyone here know what's up? Is it impossible to use FAT32 properly on these cards? Does it cause actual damage? (Can't see how that's possible, but you never know)
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn

    #2
    Re: 64GB SDXC cards and FAT32 - what's the real story?

    complex,
    those cards have evolved and i suspect back-compatability is not what it should be.
    the filesystem is irrelevent btw,
    one known problem is the supply voltage.
    some cards only work down to 3.3 or 2,.5v
    and some phones & tablets want to run them as low as 1.8v

    also the commands arent always fully implemented.
    probably some fucking asshole at the factory saying "that's obsolete - nobody uses it any more"
    resulting in a fuckload of legit Sandisk cards not working in Android devices or Nintendo handhelds!!!
    it cost them a fortune swapping those out to the customers!

    the final problem is very high capacity cards using MLC flash structure, and customers not being told how low the data retention life can be in some of them!!
    (it's months sometimes)

    personally i wont buy anything over 32gig and wont go over 16 for something that will be booting an o.s.

    Comment


      #3
      Re: 64GB SDXC cards and FAT32 - what's the real story?

      could be the partition has to be aligned to the sector size alignment of the flash card thus there is this freespace preceding the partition. the partition's cluster size and the flash's sector size being misaligned could cause read issues with the flash. could also be the software layer in the phone and the hardware layer (the controller) not knowing what to do if there is a misalignment. thus the data written and/or read becomes corrupted.

      or never trust what the chinese say. the chinese have a habit of overpromising and over-speccing on paper. so whatever they say, just take it a few notches down. if they say 64gb, only use 16 or 32 gb.

      Comment


        #4
        Re: 64GB SDXC cards and FAT32 - what's the real story?

        Interesting. I do see the Strontium card at least was rated at 3.3v while the Samsung I just bought is 2.7v-3.6v. 1.8v seems uncommon though, and I'd expect the phone to make a mention of that?
        I certainly do wonder if the higher density of the cells has something to do with it...


        As for the free space thing, I also wondered about this, however 17MB seems rather large just for partition alignment. I wonder more, if it's some reserved area for another purpose, and without that reserved space, Bad Things Happen.

        If the alignment was a problem with a translation between software\controller etc, I'd assume the entire thing wouldn't work at all and wouldn't even format. I can see it might need to re-read some sectors if clusters spanned multiple flash sectors, but that should only worsen performance, not cause actual corruption. But who knows???... it's very strange.

        For the record, I recently did reformat the Strontium card with exFAT and the 'official' SD card tool, and it made an 'empty' 17MB partition, as well as setting the cluser size of the FS to 32k.
        With my Linux-formatted Samsung 64GB in FAT32 it is also 32k, and I left the 17MB partition as it was from the factory. So, if they're both 32k...

        Funny enough, I can't full format the Apacer card anymore. It fails in about the first 200MB and drops out completely. The Strontium seems OK for now, no weird corruption like before, but write performance is weird. It does 125MB/s for the first 3GB of data, then drops (but stays steady) at 16MB/s for everything after that.


        I did do some more googling and found some interesting stuff, but I don't have the tabs in this browser right now...

        There was something about FAT32 being inefficient and with partitions over 32GB the lookup time for the files gets slower and slower, again, I don't see how it would cause corruption though, and it's not like people haven't used FAT32 on large HDDs before without issue.
        Last edited by Agent24; 08-22-2017, 05:39 PM.
        "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
        -David VanHorn

        Comment


          #5
          Re: 64GB SDXC cards and FAT32 - what's the real story?

          about reserved space - you shouldnt.
          the internal controller keeps reserved space for bad sector remapping - you will never see it.
          so any space you create is redundant.

          Comment


            #6
            Re: 64GB SDXC cards and FAT32 - what's the real story?

            There's a reason the Samsung card is double the price of the brands I've never heard of.

            Comment


              #7
              Re: 64GB SDXC cards and FAT32 - what's the real story?

              Originally posted by stj View Post
              about reserved space - you shouldnt.
              the internal controller keeps reserved space for bad sector remapping - you will never see it.
              so any space you create is redundant.
              Maybe it is just for partition alignment then? All I know is that they come like that from the factory and that the SD association's official tool puts that partition back if you delete it.

              Originally posted by diif View Post
              There's a reason the Samsung card is double the price of the brands I've never heard of.
              Indeed. I hope it solves the problem... But Apacer and Strontium are not unknown brands in NZ at least... both have been around for years. About half of my older 32GB and smaller cards are Apacer and they all still work perfectly.
              Last edited by Agent24; 08-23-2017, 02:30 PM.
              "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
              -David VanHorn

              Comment


                #8
                Re: 64GB SDXC cards and FAT32 - what's the real story?

                Originally posted by diif View Post
                There's a reason the Samsung card is double the price of the brands I've never heard of.
                Agree. Adata cards are nice too. And Lexar cards are really good. But those cost $$$.

                Originally posted by Agent24 View Post
                But Apacer and Strontium are not unknown brands in NZ at least... both have been around for years. About half of my older 32GB and smaller cards are Apacer and they all still work perfectly.
                We have Apacer here as well, but it seems to just be a brand of a large importer, as i've seen the Apacer name slapped on everything from RAM sticks to business card holders! No joke here.
                Originally posted by PeteS in CA
                Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                A working TV? How boring!

                Comment


                  #9
                  Re: 64GB SDXC cards and FAT32 - what's the real story?

                  Originally posted by Th3_uN1Qu3 View Post
                  We have Apacer here as well, but it seems to just be a brand of a large importer, as i've seen the Apacer name slapped on everything from RAM sticks to business card holders! No joke here.
                  They're an independent company and they've been around a while: https://en.wikipedia.org/wiki/Apacer

                  I've not seen business card holders, but I have bought their USB flash drives, RAM DIMMs and SD cards...
                  "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                  -David VanHorn

                  Comment

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