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Megabytes. Gigabytes. What's that all about?

When you're looking at storage devices, you'll come across the terms megabytes (MB) and gigabytes (GB). They refer to a hard drive's most important specification: its capacity. Or, to put it another way, the room to store all your stuff. To store 10,000 songs in iPod format, for example, you'd need about 42 GB of hard drive space. A 6 megapixel digital camera image is approximately 2 MB in the typical JPEG format.

How big of a hard drive do I need if I want to back up my system?

As a rule of thumb, your backup hard drive should have at least twice the capacity (MB or GB) of the computer or computers you are backing up. This gives you room to grow as you use your system. To check your computer's capacity, go to the Apple menu and select About This Mac, then click More Info... and select Serial/ATA.

What should I be looking for in a backup drive for my large media files?

If you've amassed a large collection of music, photos, and video, you should think about large capacity hard drives such as 500GB or 1TB (1TB = terabyte or 1024GB) models. Give yourself plenty of space to expand here, too—the more room you have, the longer it'll take you to fill the hard drive up.

Video files take up the most space on your hard drive—and HD video takes up even more. For uncompressed HD video, you'll need 1GB of hard drive space for every six minutes of footage. For compressed HD footage in Apple TV format, you'll need 2.6 GB per hour, while iPod format video takes up 600 MB per hour. When it comes to a hard drive for video, bigger is definitely better.

What's the deal with FireWire and USB 2.0?

They're two different ways of doing the same thing: connecting your hard drive to your computer. Each of these industry-standard connections uses a different type of jack, and both can power certain peripheral devices such as flash drives and hard drives. USB 2.0 can also power mice, keyboards, and cameras. Although USB 2.0 and FireWire are not compatible, most computers and hard drives support both kinds of connections.

How fast are these connections?

USB 2.0 transfers your data at around 480MB/sec. FireWire comes in two flavors: FireWire 400 sustains transfer speeds of 400MB/sec, while FireWire 800 blazes along at 800MB/sec.

But which one is faster in the real world?

You'd think USB 2.0 would be faster than FireWire 400. Not always, as it turns out: USB 2.0 relies on the processor of your computer and shares bandwidth with other USB devices such as your mouse and keyboard. Because FireWire is processor-independent, its speed is consistent. With devices like an external hard drive, FireWire 400 actually delivers quicker performance than USB 2.0. But FireWire 800 is much faster than the other two.

Which type of connection is best for video editing...USB 2.0 or FireWire?

If you edit video on an external hard drive, go for the FireWire 800 connection. With the fastest data transmission speeds, it'll give you the smoothest video streaming you can get from a hard drive.

I want a portable hard drive I can take on the road. What kind of connection should I get?

If you're planning on plugging into non-Mac computers, you should consider a hard drive with USB 2.0—it's a more widely used standard across both Windows and Mac. But if you're looking for quick file transfers and top-notch performance, look for a hard drive with a FireWire connection.

On the Mac, I want to use Leopard's built-in backup application Time Machine. Should I back up using USB 2.0 or Firewire?

Either one. FireWire connections will transfer data a little more quickly than USB 2.0, but with backups, you may not notice any difference. As noted, many hard drives offer both connections, so you can test out each for yourself.

Is there a way to back up a Mac notebook without having to plug in an external drive?

Apple now offers Time Capsule, a backup device that works wirelessly with Time Machine. It combines a 500GB or 1TB hard drive with a full-featured 802.11n Wi-Fi router. Even if you forget about backups, Time Machine and Time Capsule remember and work together to preserve your precious data. Of course, Time Capsule works perfectly with desktop Macs, and can be configured to backup more than one computer. So every Mac in your house or business can enjoy the simplicity of seamless wireless backup.

Can I also use Time Capsule as a wireless router or AirPort base station?

Yes. Time Capsule includes a fully functional 802.11n access point using industry-standard Wi-Fi networking and enterprise class data encryption. You can use it to share your high-speed internet access with any Mac or Windows computer—no additional Wi-Fi access point or router needed.

What kind of hard drives are best for mobile users?

One of the handiest inventions for the “road warrior” is the portable hard drive. Its small size makes it easy to carry around, and many are designed to survive the bumps and jostles that come with traveling. Their tiny dimensions mean the capacity is not enormous; most models hold between 80GB to 300GB.

Do I need to carry around a power adapter for my portable drive?

Most mobile hard drives can get power from the USB or Firewire cable directly, eliminating the need for a separate power cord. This is known as a bus-powered connection, though you may call it a major timesaver.

With hard drives, do I need to worry about formats—Fat32 vs. HFS+?

Not really. Fat32 is a Windows-based format, while HFS+ was developed by Apple for use on the Mac. A Fat32-formatted hard drive can be use by both Mac and Windows computers, while HFS+ hard drives can be used only on a Mac. The Apple Online Store sells many hard drives that are pre-formatted with HFS+. Any of these can be reformatted with Fat32, though, if you want to use them in cross-platform environments. (You'll need to back up any files before reformatting, however.)

Can I use either drive format with Time Machine?

Time Machine only works with HFS+-formatted hard drives. If you want to use your external hard drive with Time Machine, the hard drive must be formatted in the HFS+ format. (Again, remember to back up files before reformatting.)

Does a drive's RPM speed matter?

RPM refers to the “revolutions per minute” the hard drive's disc spindle revolves while reading or writing data. Higher RPM numbers result in faster data access speeds. In most cases, you don't need to worry about it. 5400 RPM is the standard speed for most portable hard drives. Most desktop hard drives offer 7200 RPM, which is plenty fast for most users.

What RPM speeds are best for video editors?

Pro users such as high-end video editors usually need even faster disk access, so they'll look for hard drives at speeds up to 10,000 or even 15,000 RPM. Though these hard drives are more expensive, they deliver the optimum performance necessary for these pro-quality projects.

What is RAID and should I consider this when purchasing a drive?

Some external drives actually have multiple hard drives in them – working as one. RAID stands for Redundant Array of Inexpensive Disks. There are many reasons for purchasing an external drive with RAID with the main ones being cost, data security and performance.

RAID 0 capability enables two drives to work as a single drive. The benefits are usually a lower price point than a single drive of equal capacity and speed advantages due to data being constantly streamed from one drive to another. RAID 0 is ideal or video editing and capture due to the increased transfer performance.

Drives with RAID 1 usually also have two drives which hold the exact same information through a process called mirroring. This provides an extra level of security in case one drive fails. While this is more reliable, the usable capacity is halved. Raid 1 is suitable for ensuring sensitive irreplaceable data has that extra level of security.

Drives with RAID 5 are often used in storage server environments and are an amalgamation of RAID 0 and 1. This is achieved by allocating one of the drives as a ‘parity’ drive therefore enabling both fast transfer speeds and backup in case one drive fails. RAID 5 is suitable for server environments where data access and 24-hour access is important.