SD card files getting deleted!

Hey guys, new Mac user here. I'm running a new MBA 13" with Lion 10.7.1 installed. Since the SSD is only 128GB, I'm using a SD card for all my mp3's, which are all loaded into iTunes. The SD card is formatted as exFAT, which was done in Lion.

Well, to my complete bewilderment, I've noticed that those mp3s are getting deleted, seemingly at random. Yesterday I checked the card, and the mp3 directory existed, but everything under it was gone. Just completely gone. Last night I spent 4 hours transferring my mp3s back over to it, setting up new directories, etc. Today, I check again, and about 3GB is missing again.

Anyone have any idea what's going on? I'm about to pull my hair out! Could this be the SD card, or is it a Mac/software thing?

Thanks!

A quick note.

When I go into Disk Utility and do a "verify disk" on the SD card, it finds a TON of problems and asks me to repair the disk. When I do that, it "fixes" everything and then leaves the card completely blank. Something about unexpected files and directories.

Maybe I should format it as a Mac OS Extended partition next time?

Anytime you use FAT, whether it be FAT-16, FAT-32, or even exFat, there is a limit to the number of entries which can be stored in the root directory. Once you exceed that number, the system will start deleting the excess. Either format the SD card to HFS+ or NTFS. HFS+ will be best in your situation.

Thanks for the tip!

The strange thing is that the mp3s weren't in the SD card's root directory. They were in a subdirectory called mp3. Does that matter?

In any case, I reformatted the card as HFS+.

Yes, the same limit goes for sub directories also. FAT can hold just so much data before it starts deleting the excess. HFS is better since it's also journaled which means less chance of data loss.

Cool, thanks. It does seem to be holding on to the files now.