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Re: SD Card Unmounted Itself...But It's Still in the Slot
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.