Is it possible to use Time Machine to back up to two external hard drives, both connected to the same MacBook? Say, one connected with FireWire, the other with USB, or the second drive daisy chained off the first?

Having multiple backup locations is always a good thing, but unfortunately, Time Machine can only back up to one drive at a time. This is because whenever you connect a new Time Machine drive, Time Machine will make a complete backup of your entire Mac. You can still achieve your goal by using Carbon Copy Cloner to automatically create a clone of the Time Machine drive on a regular basis.

This schedule will cause CCC to automatically back up your Time Machine drive every hour.

We’ve covered how to get and use Carbon Copy Cloner before, so check out bit.ly/ml_ccc for information on creating a drive clone. In the CCC interface, you’ll select your existing Time Machine drive as the Source and the extra (FireWire or USB) drive as the Destination. Then, click the Schedule This Task button near the bottom of the CCC window. Under the Schedule tab, select “On an hourly basis” from the “Run this task” drop-down menu, and then click Save. From now on, CCC will automatically back up your Time Machine drive on the hour.

If, instead, the problem is that you don’t have enough storage on your Time Machine drive to back up your MacBook, you could consider getting an external RAID solution. A RAID (Redundant Array of Independent Disks) consists of multiple hard drives in an enclosure that work together as one external drive. RAID comes in many forms, but one easy-to-use option is the Drobo—get more info at drobo.com.