Reader Ben Connolly is interested in keeping some distance between his Mac's operating system and data. He writes:

I’m planning to get a new Mac and I’d like to keep my system on one drive (perhaps an SSD) and my data on another drive. How do I go about this? Is it possible to keep my Home directory on a drive other than the startup drive?

It is. In the past you’d copy your Home folder to the other drive and then point to it via symbolic links but that’s no longer necessary. When setting up your new Mac I’d do this.

Run through the usual setup process. Once you’ve completed that process connect the drive you’d like to save your data to. Copy your user folder from the Users folder at the root level of your hard drive to the external hard drive. (You’ll have to enter your username and password to authorize this.) Launch System Preferences and choose the Users & Groups preference (called Accounts in versions of Mac OS X prior to Lion). Click the Lock icon at the bottom of the window and enter your administrator’s name and password and click Unlock.

Hold down the Control key, click on your account name, and choose Advanced Options. In the sheet that appears, click on the Choose button next to the Home Directory field. Navigate to the home folder you moved to the external drive, select it, and click Open. You’ll see that the path to that folder now appears in the Home Directory field—/Volumes/DriveB/yourusername, for instance. This is your new home folder. Anything that’s normally saved in your home folder—pictures, movies, documents, music, and preference files—will be stored here.

Test the account to ensure that it’s working properly. For example, launch iTunes and make sure that an iTunes folder is created in the Music folder within this home folder. Once you’re satisfied that everything’s working correctly, you can delete the original home folder on your startup drive.

We’re not quite finished. Return to the Users & Groups system preference and create a new administrator’s account. Why? If your external hard drive goes kablooey and your internal hard drive lacks a user folder, you won’t be able to boot that drive into a fully functioning account. With that extra account, you can.