Backin' up your Mac

Macworld - When you don't back up your data, you choose to live life on the edge. A hefty power surge, faulty software update, rampant virus or Godzilla-like toddler are just a few of the things that could leave you with a computer that's incapacitated or damaged beyond repair. But what sort of media should you use for storing your backups? You have numerous options, depending on your needs, preferences and budget.

Hard drives

Hard drives provide fast backups and restores, and external drives can be moved offsite for safe storage. But they can also be pricey. Hard drives are the only real choice for bootable backups or backing up a network, and they're ideal for archiving frequently used files when you've scheduled the backups to occur every day.

You can buy external drives with almost any combination of USB 2.0, FireWire 400, FireWire 800 and Serial ATA (SATA) interfaces. Virtually all Macs with a FireWire port (including every model sold within the past few years) can boot from an external FireWire 400 drive, making that the lowest-common-denominator choice. If you have a high-end Mac with a FireWire 800 port, you'll get faster performance from a FireWire 800 drive, but you'll pay a bit more.

SATA, a high-speed bus technology, is the fastest of these interfaces, but to hook up an external SATA drive to your Mac, you'll need to add an adapter using a PCI card (for Power Macs and Mac Pros), a PC card (for PowerBooks) or an ExpressCard (for MacBook Pros).

Only Intel-based Macs can boot from a USB 2.0 drive, but drives with only USB interfaces tend to be less expensive than those with FireWire. Note, however, that OS X 10.4 comes in two separate versions -- one for PowerPC and one for Intel. If you create a bootable backup on an Intel-based Mac, you can't use that to boot a PowerPC-based Mac (and vice versa). This restriction may disappear with OS X 10.5 Leopard.

Optical media

Recordable DVDs are inexpensive but transfer data much more slowly than hard drives, making them a good choice for files that change infrequently, such as your photo or music collection. I recommend recordable CDs only for those without SuperDrives; their limited capacity means you'll spend a long time feeding in discs and waiting for backups to finish.

Local network storage

If you want to store files from multiple computers on your network without setting up a computer to act as a file server, you can buy a network-attached storage (NAS) device, commonly known as a network hard drive. Available in both wired and wireless varieties, a NAS device is essentially a hard drive with a network interface and a minimalist built-in server -- no computer required. Turn it on, configure it via a Web browser (setting up individual user accounts and access rights, if you wish), and any computer on your network -- Mac or PC -- can store and read files on the disk. Some NAS devices use the SMB (Samba) file sharing protocol, which is the norm on Windows and also supported in OS X. Some use AFP (Apple Filing Protocol), which is the norm on Macs, and some offer both (as well as, in some cases, FTP and other protocols).

NAS is increasingly popular, and for ordinary network file storage, it's often an excellent choice. For backups, however, you should be aware of a few limitations. First, you can't run server-based backup software on the NAS device itself, so each computer on your network must run its own, individually configured backup program. Second, you generally can't use a NAS device to store bootable backups, because you can't select a conventional network volume as your startup disk in OS X. And third, some NAS devices use older versions of the SMB or AFP protocols that impose a 2GB limit on individual file sizes. This limitation can crop up, for example, when using a backup program that stores all your files inside a single large archive file. For all these reasons, I consider NAS devices less than ideal for network backups. NAS devices are available from manufacturers such as LaCie, Linksys and Maxtor, among many others.
Another category of network storage is SAN, or storage area network. Whereas a NAS device is basically a hard drive with a network interface, SAN typically uses much-higher-bandwidth interfaces, such as Fibre Channel or Ultra320 SCSI, to attach an array of drives to one or more computers. (Apple's Xsan software is a prominent example.) SAN provides extremely high throughput for tasks such as video editing and 3D rendering, but it's overkill for day-to-day backup applications.