2001: The “Read Before You Install” document on the Mac OS X install CD says that installing Mac OS X on a FireWire or USB drive is unsupported. That means it doesn’t work, right?

Nope, it means your 90 free days of tech support isn’t valid. Big difference! If you’re willing to forgo your 90 free days of listening to Muzak, ahem, 90 free days of Apple phone support, here’s how and why you should install Mac OS X on an external FireWire drive.

A consumer-level system that can run Mac OS X, such as an iMac, iBook, or G4 Cube, only supports one internal drive at a time. What if you have lots of important financial documents or a music collection that took 15 hours to download stored on your internal hard drive?

If you partition your internal hard drive, as is strongly recommended for installing Mac OS X on a single drive, all of your data will be lost.* If you install Mac OS X onto your existing system without partitioning and anything goes wrong, you could lose all of your data anyway!

Benefits of an External Drive

But you’ve got FireWire ports (at least on the latest models)! When you’re ready to buy Mac OS X, get an external FireWire hard drive with it – they start at around $200. Here are the benefits:

• No worrying about making backups or partitioning. If you don’t even know what partitioning is, this setup lets you avoid it.
• It works just like a second drive. You get to keep all the free space you have now on your internal drive.
• Portability. You can bring your hard drive over to your friend’s house and run Mac OS X on their Mac without having to install anything on their computer! Great for showing off how great you are, ahem, how great Mac OS X is.
• Performance. Many FireWire hard drives are faster than the one that came with your Mac. The slowest currently available FireWire hard drives are about the same speed as the drives shipping in iBook and PowerBook G4!

The installation process is as easy as installing Mac OS X on your internal drive, with the driver software needed for controlling the external drive already built into the OS.

The only known issue occurs after installation with some drives: You cannot select the FireWire drive in Mac OS 9’s Startup Disk control panel to boot back into Mac OS X – it looks “grayed out”. If this is the case, restart your Mac and hold down the Option key. This opens the Startup Manager. You can then choose the FireWire drive and click the arrow to continue starting up into Mac OS X.

Updating the Startup Disk control panel to version 9.2 usually solves this problem.

Picking a Drive

What kind of drive should you use?

I bought a discontinued 6 GB VST Portable FireWire drive for a decent price. It’s neither the fastest drive nor the least expensive per gigabyte, but I like it because it’s cute, because VST has seamless Mac OS 9.1 support, and because it’s powered by the computer. Almost all currently shipping FireWire hard drives are advertised as bootable in Mac OS 9.1 and thus work for Mac OS X as well. Check with the manufacturer if they don’t advertise this feature.

What computer do I need for this to work?

All Macs with built-in FireWire except for the Blue and White Power Mac G3 and the “Yikes” Power Mac G4 will work fine.

What About USB?

I don’t have FireWire on my computer; will USB hard drives work?

Yes, but they’re very, very slow.** On average, USB hard drives are 1/20th the speed of FireWire drives with the same drive mechanism, or close to the speed of a floppy drive. Veteran Mac users know that booting off of a floppy takes several times as long as booting from a hard drive – and that was when the OS could fit on a 1.4-megabyte floppy. Mac OS X takes up over 1000 megabytes! The only Macs that didn’t ship with FireWire ports that can boot from USB are the 350 MHz iMacs and the original iBooks.

You will need to hold down the Option key while booting to select the USB drive.

Running Mac OS X on an external FireWire drive is just as easy and responsive as running it on your internal hard drive, with no problems short of losing that free Muzak. Darn!

 * This was written when Mac OS X 10.0 was new, long before Mac OS X 10.5 Leopard added the ability to repartition a hard drive without wiping out your data.

 ** This was also the era of USB 1.1. USB 2.0 is 40 times as fast and still considered painfully slow when booting – but it’s much better than USB 1.1. FireWire 400 tends to run a bit faster than USB 2.0, which wasn’t an option on Macs in 2001.