[sanford]

I have a Lexar 512MB USB 512MB Jump Drive, a USB flash drive. When I first plugged it in, Finder info showed 488MB total capacity with 170.1 MB in use, althought absolutely nothing was on the drive that I could see or had put there. So I formatted the flash drive with Disk Utiity. In Disk Utility I've formatted it both "MS-DOS" and "MS-DOS (FAT16)". When I partition/format it shows it will format to something like 498MB. Then in the Finder it shows as having that same and expected 488MB total capacity. I know that due to formatting overhead and byte-size calculations storage media will never have quite the actual, usable capacity stated in the manufacturer's specifications. But whenever I've copied about 318MB to the Jump Drive, it shows 488 total capacity, 170.1 free, but no more data will copy to the Jump Drive, giving me a message that file couldn't be copied because the drive is full.

I'm wondering if the "MS-DOS" partition format option in Disk Utility is really FAT32, or if it's not, if I should try booting into Windows XP and formatting the Jump Driver as FAT32 and see if that helps (I don't get a FAT32 option in Disk Utility). I can try formatting in Disk Utility with one of the many Mac OS X options and see if that helps, but I'm primarily connecting this flash drive to my MacBook and an Xbox 360, and I don't think the 360 will read any Mac OS X or straight UNIX disk formats.

Any help would be appreciated. It's possible the drive is defective, I guess, but it sure doesn't seem so. I'm not getting any read/write errors, the drive formats fine, up to 318 MB of files copy over fine, uncorrupted and quickly, and the Xbox 360 recognizes the drive immediately on start up and play MP3s and unprotected AACs off the drive just fine, no problems. I certainly don't mind getting only 488MB capacity out of my 512MB flash drive, but I think 317MB is a little weak.

[sanford]

Here's the fix, for people in my situation, who want full access to all 488MB accessible on a 512MB Lexar USB flash drive, but you need it readable by an Xbox 360 or a Windows PC: no MS-DOS partition, FAT16 or FAT32, will work. It has to be a Mac OS X format, like Mac OS X Extended or the same, Journaled. The trick is under options in Disk Utility set the partition table type to Master Boot Record. This allows your Mac to write to the whole available 488MB and still lets your Xbox 360 or Windows PC read the flash drive. Works like a champ on my 360.

[ghporter]

That "fix" could ruin the cross-platform functionality of USB flash drives. An MBR format should Considering that you can find 1GB flash drives for around $25 most of the time, that minor "formatted capacity will be smaller than stated raw capacity" issue isn't a real concern for most of us. And I got by for a couple of years with a 128MB flash drive, using it at school for ALL my papers and assignments... When I moved up to a 1GB drive, it felt like I was in a huge, empty warehouse when I looked at its contents.

The "MS-DOS" format is actually "FAT12", the same format Windows uses for floppy disks. AVOID IT! Like FAT16, it uses relatively large, fixed cluster sizes, so you waste a lot of disk space unless all your files are just under a multiple of the cluster size. For example, with a 16k cluster size, a file of 15.9k will take up one cluster, or 16k on disk, but a file of 16.1k will take up TWO clusters, or 32k on disk. LOTS of waste there. FAT32 uses smaller clusters (I think the default is 4k) and allows for different cluster sizes. It's a much better choice-and it's cross-platform compatible.

Unless you need to move and store huge files, the formatted drive "capacity loss" is relatively trivial.

[sanford]

Originally Posted by ghporter 

That "fix" could ruin the cross-platform functionality of USB flash drives.

Umm... What? Formatting with MBR as the partition map preserves the cross-platform functionality of the USB flash drive. Windows PCs require the MBR partition map, or 3rd party Mac drive format reading software, to read the volume; Mac OS X natively reads MBR partition-map (MS-DOS) volumes. So it works on a Mac, works on a Windows PC, even works on an Xbox 360. That sounds like cross-platform to me. What you can't do is *boot* a Mac from the flash drive with MBR and since that was never my stated purpose, who cares? If I wanted an emergency boot flash drive around I would keep one solely for that purpose, and it would have to be GUID which wouldn't cross-platform boot a PowerPC Mac anyway.

As I said, FAT16 and FAT32 would not work; the Mac still could not access the full drive capacity. 170MB of capacity loss on a 512MB (488MB formatted) volume is not "relatively trivial". It's an entire third of the formatted capacity. As an analogy let's say, generously, that one's IQ is 140; in order for some unexplained convenience or another, like stunning good looks or the like, you accept to trade away one third of your IQ. Your IQ is now 94. You are now very pretty but too stupid to use it to your advantage. Doesn't sound like a good deal to me.

I love it how you post a question, no one has a clue how to fix it, doesn't post to help you, you fix it yourself, you post the fix in case someone else runs into the same problem, then all these so-called informed heads start popping up to incorrectly claim your fix won't work. Love it, love it, love it.