1. AC Question's Avatar
    I recently bought a new Motorola G 3rd gen and a Samsung 64gb SD card to go with it and everything has been fine for the month I've had it but last night I noticed some apps where grayed out and it said 'SD card unexpectedly removed' I switched the phone off and then on again and it was fine. This morning exactly the same thing happened but when I turned the phone back on it said that my SD card was blank or has corrupted files on. I'm currently on holiday and don't want to lose all the information and pictures I have.
    Does anyone know why this would have happened and what I can to do fix it please?
    10-15-2015 05:28 AM
  2. B. Diddy's Avatar
    Welcome to Android Central! Although SD readers can malfunction, the more likely problem is that the card itself is defective or counterfeit. Counterfeit SD cards continue to be a fairly common problem, especially if you purchase from relatively unknown online sellers. Run SD Insight to see if your card is valid.
    Laura Knotek likes this.
    10-15-2015 01:18 PM
  3. hexed01's Avatar
    i was having the same probleme with my moto g and got this replay

    Guys, it's not the card - it's the Class 10 rat ing. You want a Class 2 or Class 4, but nothing higher than 4. You don't want high read/write speeds, you want high Random Access response times.

    Class 10 = High Write/Read, Very Low Random Access response times.
    Class 2 = Low Read/Write, Very High Random Access response times.

    It's a give or take, but not both. You don't want high read/write speeds on sdcards, they are all very slow anyways.

    Class 10 cards are for digital cameras that has 10 to 20 MB of data to write as fast as it can. They are not for mobile devices.

    All mobile devices (Windows Mobile, Windows Phone 7 (my personal hacks), multiple Androids, etc) all have built-in "timeouts" for request queues when reading/writing to a device (e.g. sdcard). This is because mobile devices are synchronous, with only a single device able to read or write bits at a time. Eveyrthing goes into a "queue" waiting to read/write, and everything has a timeout in that queue.

    I had all sorts of issues with Windows Mobile and Android phones in the past, but they still worked mostly. Until I got my Windows Phone 7 two years ago and immediately opened my HTC Arrive to replace the 16 GB Class 2 card with a 32 GB Class 10. Immediate crashes, reboots, etc followed. Returned the card, got a new one, same thing.

    As it turns out, a local Microsoft rep told me the secret: Windows Phone 7 operating system has "stricter timeouts" for the storage queue (read/writing). They require extremely low Random Access times to shave 50% or more "milliseconds" from the response of WP7's GUI. That's what makes WP7 so "snappy" with instant touches.

    That made perfect sense! I since purchased a SanDisk Class 2, stuck it into my HTC Arrive, and had zero problems. The device was rock solid, and very very fast. I have since purchased Class 2 and Class 4.

    The problems that Microsoft had with the first batches of WP7 devices was that no one could produce an SDCard with a low-enough response times. SanDisk was sold out of the Class 2/4 16GB sdcard cards for 3 months, which delayed a large amount of WP7 phones from being shipped.

    Just want to reiterrate that I have since purchase 6 or 7 Class 2 and 4 cards rangomg from 16 GB to 64 GB, and they have all worked flawlessly for my devices and all friends' devices that asked me which card to get, including on friend with a Galaxy Note 2 and a 32GB Class 2 card.
    10-22-2015 04:42 AM
  4. theundead176's Avatar
    So I ran the app and it doesn't identify the manufacturer of the SD card. Does it mean that the card is fake? It's an old card, 8gb Kingston (supposedly) class 4.
    Should I get a new one or try formatting it first? I only keep music on the SD card
    10-25-2015 12:57 PM
  5. michaelkenney's Avatar
    I just ran SD Insight to confirm that I have a San Disk 32GB card, which is class 10. I have reset my phone (BLU Studio 5.0C), changed the card (to a Toshiba 16GB class 10) and my phone is still constantly asking me if I want to change the default write disk. The only way I have been able to stop it happening is to just remove the card, which I am ready to do again.
    It wouldn't be so bad, but the system only has one notification sound and I have yet to find a way to turn off the notification that my card has unmounted. I only want notifications of texts coming in. I have turned off every notification I can find, but still get so many that I often miss texts as I am so used to my phone beeping at me for nothing that I ignore it.
    Just_Some_Nobody likes this.
    11-07-2015 01:51 AM
  6. michaelkenney's Avatar
    PS: It has done it twice while I was writing this.
    11-07-2015 01:51 AM
  7. divinemyth99's Avatar
    Class 10 = High Write/Read, Very Low Random Access response times.
    Class 2 = Low Read/Write, Very High Random Access response times.

    It's a give or take, but not both. You don't want high read/write speeds on sdcards, they are all very slow anyways.
    This is just not true. The truth is that random access times are not something that's measured at all when classifying SD cards. The Class rating tells you absolutely nothing about random access times. Some Class 2 cards are slow all around and some Class 10 cards have both high sequential and random times. Here's a benchmark from Tom's Hardware in 2011. Even if you don't read the text, you can see from the very prominent chart that the card with the fastest random time happened to be a Class 6 card, beating out all of the class 10 cards. But the card with the WORST random access time was ALSO a Class 6 card.

    To re-iterate: The only way to know anything about the Random Access performance for the SD Card model you purchased, you have to look at benchmarks or perform your own. SD Cards are only rated (class) for sequential performance.
    09-26-2016 08:08 AM

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