How Should You Format Your External Hard Drives and USB Flash Drives for Macs?How Should You Format Your External Hard Drives and USB Flash Drives for Macs?

Its amazing how USB flash drives  sometimes called thumb drives  have replaced floppy disks as the most convenient way to transport data. They're small, sturdy, fast, reliable, and hold a heck of a lot of data.I keep a 4GB flash drive in my briefcase. Its often the best way to share data with colleagues. Can you put a copy of your presentation onto this, Ill ask after a meeting, holding out the flash drive. Its hard for people to say no.

I also keep a couple of much smaller throwaway flash drives in my briefcase. I have a whole bunch of 32MB, 64MB and 128MB flash drives that Ive been given at conferences. Theyre good for putting data onto, handing to someone, and saying, Just keep it. They're not good for much else.

Because flash drives are commonly shared between Macs and Windows PCs, I suggest that you keep flash drives in the cross-platform FAT32 for Windows format. Thats the Windows-specific format that flash drives come from when you buy them from the store. The last thing you want is a flash drive that you can't share. Fortunately, Macs read/write FAT32 drives very well.

Nearly every external hard drive Ive come across also comes preformatted as FAT32 for Windows, which also makes it cross platform. However, many external hard drives will be used exclusively with just one type of computer, either a Mac or a PC. (That's not always true, but it often is.)

If you are giving an external hard drive to a Mac user, and you know the drive will be used only with Macs, he/she will achieve greater performance  and better data integrity in case theres a power failure while youre using the drive  if it is reformatted as Mac OS X Extended (Journaled).

You can read all about journaling from Apple, in Mac OS X: About file system journaling.

Important note: If you reformat the drive, youll lose all the data on it  reformatting also erases a disk. So, make 100% sure the disk is empty first, or that any data on it can be safely discarded. Also, if you reformat as Mac OS X Extended, the drive will not be readable by any Windows PCs if you plug the drive into the machine directly. You can, of course, share it across the network, if the external hard drive is attached to a Mac, and if the Mac is configured for file sharing.

You can reformat the external drive using the Disk Utility, which is in /Applications/Utilities.