By Joe Hutsko, Barbara Boyd

With the advent of flash drives and remote storage, this topic is almost obsolete. In fact, the newest Macs — even iMacs and Mac Pros — don’t come with optical disc drives; you have to use an external drive to write files to CDs or DVDs.

But perhaps the biggest drawback of backing up to a CD or DVD is the space limitation: CDs can store up to 700MB of data, single-layer DVDs can store 4.7GB of data, and dual-layer DVDs store up to 8.5GB of data.

A dual-layer disc employs a second physical layer within the disc, which the drive accesses by shining its laser through the disc’s first, semitransparent layer.

If you need to back up only word-processor or spreadsheet files, a single CD should be sufficient. However, music, video, and digital photographs take up more space, which means that you may need to use several DVDs to back up all your files.

The more discs you need to back up your files completely, the harder it is to keep track of all the discs — and the slower (and more tedious) your backups are to make. This can cause you to not back up your data as often as you should; eventually, your backup files fall too far out of date to be useful, which defeats the purpose of backing up your data.

So, if your data frequently exceeds the storage limits of a single CD or DVD, you should probably rely on a different backup method.