If you’ve come to the realization, like I have, that a Mac is indeed a PC (in the sense that it is a personal computer) and you’ve decided not to limit your computing experience to one camp, then you might have come across issues with sharing data between Windows and OS X.

If you use Windows 7 and OS X Lion (or Snow Leopard), you can create a Truecrypt volume that can support files larger than 4GB and has read and write capabilities in both operating systems using exfat. I’m not sure when exfat support was added to OS X, but I believe 10.6.4 has limited support and 10.6.5 expands the support for all Macs.

You can add support to Windows XP with this KB, but I have not confirmed that this works.

Windows 7 has native support for exfat.

MacDrive

There are a lot of solutions to sharing data between OS X and Windows. One solution is MacDrive. It’s $50 and installs on your windows PC. This allows you to mount Mac drives that are formatted in HFS or HFS+ in Windows XP/Vista/7/2008. It supports read/write operations and can format or attempt to fix a corrupted mac formatted disc. I own this software, but I feel that it’s operation is rather mediocre. It crashes Windows Explorer often and it has some serious issues transferring large files.

Don’t start blaming Windows for the issues either. Windows 7 is almost as stable as XP SP3 these days and crashes a few times a year for me (I can’t even tell you the last time I saw a BSOD). The few crashes in Windows that I have are usually due to poorly written device drivers or sometimes it’s because I’m pushing the system to its limits and Windows doesn’t crash, per se, but takes an inordinate amount of time to respond and I hit the magic reset button. I’m not a patient one… All that being said, if MacDrive works for you, great, but it doesn’t fit my needs

Ok, enough complaints; to the solutions.

Truecrypt

Windows and OS X support a disc format called exfat. The first thing you want to do is format your drive as exfat. Windows will only format a drive as exfat if windows recognizes it as a removable drive. Currently, you can’t boot to an exfat formatted drive.

If windows recognizes your drive as removable, you should have a exfat format option like the picture shown.

Once you’ve formatted your drive, we’ll need to create a Truecrypt container to keep our encrypted files.I’m not going to get in to a lot of details about creating a Truecrypt container since you can get all that info on the Truecrypt web site. You’ll want to create a new volume and then mount it. It doesn’t matter if you choose NTFS or FAT for the Truecrypt formatting since we will be reformatting it later, but I’ve found that NTFS seems to format faster that FAT in Windows.

Format Truecrypt as exfat

Once you’ve created your container, mount it as a drive with Truecrypt. If you attempt to format the drive in the Windows GUI, you’ll notice that your only options are NTFS and FAT (since Windows thinks Truecrypt volumes are internal drives). FAT will give us read/write support in both operating systems, but it won’t be able to support files larger than 4GB. NTFS can support files larger than 4GB, but it has poor read/write support in OS X (even with NTFS-3G).

Command line to the rescue

We can, however, format the volume from the command line. Using the following command:

format <DRIVE LETTER>: /FS:exfat /Q

Format is a pretty basic command. Replace <DRIVE LETTER> with the drive you want to format. The /FS:exfat tells format what format you want the drive to be (if this wasn’t obvious) and the /Q tells format to do a quick format. I haven’t found a compelling reason to not quick format the drive - which takes significantly longer, especially for large drives. You may have to run cmd as and administrator. You can either right-click and choose Run as Admininstrator or you can hit the windows key on your keyboard, type cmd and hit ctrl + shift + enter to run as administrator.

Truecrypt drive that is mountable in Windows 7 and OS X

And Robert’s your mother’s brother. Now you have a Truecrypt volume that you can mount in Windows 7 and OS X that has large file support and native read/write support in both OSes.