1. DennisOS2's Avatar
    There are wide varieties of comments on many boards about memory cards for use in phones and tablets. The comments/pleas cover either use of SDs in different brands of phones/tablets; ability to use various sizes of cards; intermittent ability to read from or write to cards in the same phone/tablet at different times. It would be great if we could get an expert on this subject to instruct us on the proper handling of the SD cards so users could enjoy consistent functionality from the cards. I'd like some basic questions answered:
    1. What really determines (in any given phone/tablet) the maximum SD card size that device can use? Is it hardware or software (OS).
    2. What can cause corruption of the cards? What can be done to minimize corruption?
    3. Where should cards be formatted to maximize functionality within and between devices? In the device or a PC/MAC?
    4. Is there really a difference between card manufacturers and reliable use? That concept is thrown around but seems to be more anecdotal than based in real testing.
    5. Is there an inverse relationship between size of the card and reliability (readability and potential for corruption)?
    6. Most know that these cards should be 'unmounted' before removal from a running device. What is likely to or might happen if the card is not unmounted? Under what circumstances should must the cards be unmounted?
    04-28-2015 10:23 AM
  2. Rukbat's Avatar
    1. What really determines (in any given phone/tablet) the maximum SD card size that device can use? Is it hardware or software (OS).
    A combination.
    2. What can cause corruption of the cards?
    Pulling a card our without dismounting it. A defective card. A counterfeit card. (If the card has a memory chip that's 4GB, and the card is programmed to say it's 32GB, as soon as you try to write more than 4GB to it, you corrupt it.)

    What can be done to minimize corruption?
    Unmount cards before removing them (that includes "Safely remove ..." in a Windows computer). Buy SanDisk. (Samsung messed up around the time Jelly Bean came out with the S3 - it corrupted cards. SanDisk modified their cards to work in Samsung phones. Samsung didn't. [Samsung replaced the bad cards even though it wasn't their problem.])

    3. Where should cards be formatted to maximize functionality within and between devices? In the device or a PC/MAC?
    In the device. PCs and laptops don't add the folders the Android device needs. However, cards very rarely need formatting.

    4. Is there really a difference between card manufacturers and reliable use?
    Chip manufacturers or card manufacturers? There are only 2 chip manufacturers for the chips in the cards, Samsung and Sandisk, Everyone else buys chips from them and makes cards. Samsung is okay, but I've been using SanDisk memory devices since they came out with them (I believe they were called SunDisk back then) and the oldest ones I have [32MB - that's not GB) still work. Not too useful, but still working decades after the warranty expired.

    That concept is thrown around but seems to be more anecdotal than based in real testing.
    You can't have an actual 25 year test of a device that's only been out for a few months, and the size of the cards (and the hardware and software design in them) changes every time. All you can have are anecdotal "evidence". (Testing a few hundred cards for the equivalent of 10 years would cost a small fortune. Nevertheless, SanDisk has enough confidence in what they produce that their cheapest cards are guaranteed for 5 years.)

    5. Is there an inverse relationship between size of the card and reliability (readability and potential for corruption)?
    All other things (like the ability of the device to handle the particular card type and size) being equal, no.

    6. Most know that these cards should be 'unmounted' before removal from a running device. What is likely to or might happen if the card is not unmounted?
    You could corrupt data especially if the card is still being written to as you remove it, or you could blow the hardware in the card.

    Under what circumstances should must the cards be unmounted?
    When the device is turned on. You can remove a card from a phone that's turned off without dismounting it (because you can't dismount it.) IOW, under all circumstances. 99.999% of the time, not dismounting the card won't hurt anything. That doesn't mean that you won't blow the card the first time you try it (then have no problem the next 9,999 times). If you don't want to buy a new card (and possibly a new device), unmount the card. In a computer, you could blow the USB port if you remove the card without "unmounting" it - it depends on the port's hardware. At the very least in a Linux computer (which an Android device is), you should umount the card, so the operating system doesn't go looking for it and hang. (That's from the software side - unmounting the card hardware unmounts it too.)
    B. Diddy likes this.
    04-28-2015 06:08 PM

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