Upstream Internet bandwidth is a scarce commodity, as is computers' computational power. The software we tested all allow various measures of throttling upstream (and sometimes downstream) bandwidth use, but most have poor controls over scheduling active times for backups.

Most of the software lets you choose one or more of these parameters: time of day to start making backups; time of day to stop making backups; how many minutes of idle time before starting a backup; how much processor power to use while backing up; bandwidth limits for upstream traffic; frequency of backups.

Software that looks to start backups when your computer is idle uses either or both minutes of inactivity and CPU usage, as thresholds to start backing up or unthrottle a backup to full speed. Some software lets you set a maximum percentage of CPU usage that the program can occupy, too.

As with other factors, no two backup packages offer the same options. And unlike desktop backup software, you can't schedule different sets of backup files if you wanted, say, a critical set of folders to be archived every four hours, while music and movies are uploaded only on weekends. This is a terrible omission, having been available for local backups since at least the early 1990s, but unfortunately common to all the tested offerings.

Jungle Disk offers the closest option: you can set up multiple backup volumes--which are essentially like folders at Amazon's S3 and Rackspace--and each can have its own backup selection and schedule.