External Options for Upgrading Your iMac Hard Drive

By Mark L. Chambers

If you need additional hard drive space for your iMac, consider using an external drive. Use a high-speed Thunderbolt 2 or USB 3.0 port to connect a second hard drive the quick and easy way. (Owners of slightly older iMac models can use FireWire 800 as well.)

Today’s Thunderbolt and USB peripherals don’t even require the driver software that Mac old-timers remember with such hatred. You simply plug a device into one of these ports, and it works. And you can move your external drive between different Macs with a minimum of fuss and bother.

An external hard drive can do virtually anything that your internal hard drive can do. You can boot from it, for example, or install (and boot from) a different version of OS X (great for beta testers).

Apple’s Time Capsule unit is an external hard drive with a difference: It stores the huge Time Machine backup files created by the Macs running OS X on your network, and it uses a wireless connection to transfer data! (In fact, if you’re thinking of adding a wireless base station to your wired network, your Time Capsule actually acts as a full AirPort Extreme Base Station, complete with USB port for connecting a USB printer.) At this writing, Time Capsule is available with a 2TB ($299) or 3TB ($399) drive.

Here’s one problem with external drives, though. Even USB 3.0 connections transfer data more slowly this way than via an internal drive (only the newer Thunderbolt connections rival the speed of an internal drive). That’s why most Mac owners (especially graphics and video professionals) use their external drives for storing backups, digital media, and little-used documents and applications. Their favorite applications, work in-progress and often-used documents are housed on the internal drive.

Current iMac models carry two kinds of high-speed ports, either of which is a good match for connecting any external device.

USB 3.0

The USB standard is popular because it’s just as common in the PC world as in the Mac world. (Most PCs don’t have a Thunderbolt port.) Your iMac carries its USB 3.0 ports on the back of the case, which are fully compatible with older USB 2.0 devices. Hardware manufacturers make one USB device that works on both Macs and PCs.

If you’re using an older iMac with USB 2.0 ports, there’s no need to spend extra money on USB 3.0 devices, because you won’t get the performance boost. ‘Nuff said.

FireWire 800

Current iMac models no longer carry a FireWire 800 port, but if you’re using an older iMac (without a USB 3.0 port), you’ll find that a FireWire 800 drive offers much better performance than either a FireWire 400 or a USB 2.0 drive.

The physical FireWire 800 connector is shaped differently than an older FireWire 400 port, so don’t try to force the wrong connector into the wrong port!

Thunderbolt 1 and 2

Talk about raw speed. A first-generation Thunderbolt connection provides a blazing 10Gbps, which is twice as fast as USB 3.0 — and the latest iMac models sport the Thunderbolt 2 port, which doubles that transfer speed to an unbelievable 20Gbps! You can use a Thunderbolt port to connect an external hard drive or even a high-resolution monitor or HD-TV. Luckily, the price for Thunderbolt external drives has dropped significantly since the port first appeared on the Mac, so you no longer have to pay a premium price for Thunderbolt devices.