This article was written by a Mac user that has just reformatted his USB drive. It was just done by accident, but it is still worth reading.
The good news is that it is possible to reformat your USB drive. The USB format tool does not overwrite any of the data on your USB drive, so if it doesn’t work after reformatting, you should be able to restore all of your files and data back to the way they were before.
I have reformatted a USB drive before and I can confirm my files and data are still where they were before doing so. If the USB format tool worked, you would have to restore all your data. With the new tool, you can only restore your data, not your files, so the only way to restore your files is to reinstall your Mac.
This is kind of a simple fix, but when I first reformatted my USB drive to FAT32, everything was wiped clean without warning. When I reformatted it back to NTFS, then did a full scan, all the files and data were gone. My Mac is still on the same USB drive.
When I first reformatted my USB drive, I noticed I had 3.2 GB of data. After restoring my data, I found that I only had 1.4 GB of data, which still doesn’t make any sense. I guess it is because I had 3.2 GB of data when I first reformatted my drive, but then I restored my data, and all my data was still on that 3.2 GB.
That’s because when you reformatted, the USB drive was only formatted as one “sector size”, which is 512 bytes. This drives the information into a block, which is a number of bytes that can be written to a file of any size. So when you reformatted, your USB drive was taking up one block of 512 bytes, which didn’t work.
It’s true that reformatting your USB drive is a bad idea because it might overwrite files on your computer. It’s also true that you can reformat the USB drive to any size you would like. The problem is that you are only formatting one sector size, and you cant format the USB drive to be any smaller. So that is why usb drives are formatted as one sector size, and not a multiple sector size like a hard drive.
Well then, if a USB drive is formatted as one sector size, then USB drives are no longer FAT. USB drives are FAT, but they are still one block of 512 bytes. This means that you can reformat the entire USB drive to whatever size you want without the risk of it overwriting anything. That’s a plus.
So if your usb drive has been formatted as 512 bytes, then that means you can use any usb drive to backup your files to an external hard drive. That is cool.
Not so cool, though, is the fact that if you reformat the usb drive to a multiple sector size, you can only use any usb drive to backup your files to an external hard drive that is formatted at the same multi sector size as the usb drive. Hence, if you have a usb drive formatted as 512 bytes, and you reformat it to a multiple sector size, you are stuck with only a small part of your files on the usb drive.