Compression

Even optical discs and hard disks seem to keep getting bigger, keeping backups small still crops up as an important issue. Most, but not all, backup software offers compression as an option; sometimes even image-based backup software offers compression. This section will describe some of the situations where you might need this feature.

The most obvious need for compressed backup is because you just don't have enough space. For example, your digital family photo album that no longer quite fits on a recordable CD, might easily fit if your backup software can compress the data before storing it. And just because the stuff you want to backup fits easily on a recordable disc, doesn't mean that your backup will. For example, a feature like versioning (retaining the most recent several versions of each backed-up file) can easily balloon the amount of space your backup requires.

Another place compression becomes important is for online backups -- copying your backup data across the network (be it Ethernet, DSL, cable, or phone line). The bigger the backup is, the longer it's going to take to copy the data across the wire. Most companies that sell online backup services make you use their own software, which invariably uses compression to help reduce the bandwidth they have to pay for to service so many customers at once. But even the home user copying a backup archive to their ISP's disk space for safekeeping may appreciate having compression to save time.

Many of the low-end backup software packages that support compression do so by creating backup archives in the popular Zip file format. Although that file format is not without its limitations, it has the advantage that lots of software for viewing and manipulating .zip files already exists. If you already own a favorite Zip application for Windows, then you may want to select backup software that can store its backups in that format.

VersioningSoftware Buyer's Guide