[Galaxy Note II Android Development] TerraBuzz:
Hi betoNL, how are you...? :)

This explanation might help you to choose your sdcard file format.

1. The main difference of FAT32 & exFAT is in it's maximum file size. FAT32 only support 4GB of maximum file size per file, while exFAT support for much larger 64 ZiB (Zebibyte) per file. This means, you cannot copy a single 6GB .mkv movie into a disk partitioned with FAT32 for example.

2. The second purpose of exFAT file format is in it's seamless interoperability between Windows and OS X platforms. By default, you can not read and write an NTFS formatted disk on Mac. You have to format it in FAT32 to be writable in Mac, but then you're limited to 4GB file size. exFAT is a solution for this, you can R/W on both platforms without losing the ability to store large files.

Though there are many other features of exFAT, those two are the only big reasons for many people to use exFAT.

Since Android is coming from Linux branch, the file system we are using is ext.2, 3, & 4. Unfortunately, these formats are not supported directly by both Windows or MacOS. We have to emulate these with some kind of drivers to be read/writable on those OS. Back in the days of Gingerbread and below, we know UMS to read & write files into our phone. But one of the drawback was, we can not use our phone to access our storage while on that mode. Now we are using MTP to do this, but we are still limited to only read media partitions like Gallery and it's slow transfer rate issue. Alternative for this, is using WiFi to transfer files between our phone and our PC.

Back to your question, here's my story with a Team 64GB UHS-I sdCard. I'll start with some facts I've found during my experience:

1. SdCard with capacity more than 32GB come preformatted using exFAT.

2. If I put a 32GB sdCard or below into my phone then format it using my phone, it will be formatted as FAT32. But if I put a 64GB sdCard and then I format it inside my phone, it will be formatted as exFAT.

3. Windows can format a 32GB disk using FAT32, but it can not format a 64GB disk using FAT32. You won't have any option inside Windows to format it as FAT32 if your storage capacity exceed 32GB.

It seems like I was forced to use exFAT when I decide to use 64GB sdCard, so then I used exFAT for a while without reformatting. But then I've experienced some issues using exFAT. One of the issue I could remember was my phone running slower, especially when accessing files. It was noticeable from the boot up, to scan media storage took longer than before. But I thought it was because of it's bigger capacity. At that moment, a 64GB sdCard was rarely used, so I didn't try to find the answer.

Until one day, I've decided to try custom CM based ROM for my phone, I was shocked, my 64GB sdCard was not detected after flashing a PA ROM... Not just my files were gone, my phone was also not able to find my sdCard anymore... It was corrupted... :crying:

According to this: http://forum.cyanogenmod.com/topic/74513-why-doesnt-my-sdcard-work/, an exFAT File System is not yet completely supported on CM since it is a proprietary file system from Microsoft. That's why, I ruined my sdCard since the beginning of flashing process in recovery... lol...

Since then, I've decided to use FAT32 rather than exFAT. It runs faster, and I am free to try many ROM base. Of course I'm limited to smaller file size, but in my opinion, it's not that crucial to store files larger than 4GB in a phone for this moment. I can always convert my videos to other file formats and settings to reduce their size, without sacrificing their quality that much since I only watch them on a phablet.

So, it is for you to decide. Are you going to store large files? If not, I suggest you to format your sdCard using FAT32.

Here's another link from Wiki to help you understand more: https://en.wikipedia.org/wiki/ExFAT. You'll find many things to consider, especially in the "Advantages" and "Disadvantages" section. :)

If then you decide to go with FAT32, here's what I have done to repair mine:

1. Use any partition tool, they're usually support multiple file formats. I was using a free, small, easy to use software called 'FAT32 Format'. You can download it here: http://www.ridgecrop.demon.co.uk/index.htm?guiformat.htm or here: http://fat32-format.en.softonic.com/

2. Format it using an sdCard reader in Windows with that tool.

3. About allocation unit size, it depends on how you want to get the speed or space. "The lower the allocation size, the more space you have, but accessing the files will be slow and vice versa. Allocation units are the granularity with which disk space will be allocated to files, so if you have a 4k allocation unit, a 1k file will be allocated 4k, and a 10k file will be allocated 12k. A smaller allocation size will give less "wasted" space, but will also be slower to access (actual data) due to increased MFT/FAT access. The default unit allocation size is a good balance between space and speed, so my advice would be to stick with 4096 bytes." More on this, here: http://www.tomshardware.com/forum/249024-32-allocation-unit-size-formatting-500gb. My sdCard is formatted with 4096, but my 2TB external harddisk drive is using 32768.

4. Your sdCard will be ready to use, don't format it again inside your phone

5. Good luck ;)

PS: Sorry for a long post and explanation, I hope this is useful, cmiiw... :D