To firefighters, a Backblaze is a fire that has been deliberately set to protect a forest by depriving the blaze of fuel. Computer users should think of Backblaze as a way to wall off their key files from all sorts of disasters.

The heart of the application is Backblaze's Control Panel, which can be started from a Task Tray icon. The interface puts key information up front, showing when the last backup was made and what files are waiting to be sent. There are buttons for backing up now, restoring data and changing the software's settings.

Backblaze offers unlimited storage capacity, but the service limits what types of files can be archived. Unlike the other services reviewed here, Backblaze specifically excludes a whole series of file types. By default, the service saves all user files such as music, photos and emails, but ignores system, program and Windows files, although you can put some file types back into the backup mix, such as Windows or program files.

You can set Backblaze backups to be continuous (where it's backing up to the cloud whenever your files are saved or changed), performed on a schedule or done on demand. Although the service can back up the contents of an external hard drive, Backblaze doesn't include the ability to back up the entire system to an external hard drive as three of the other services reviewed here can.

Unlike Mozy and Carbonite, Backblaze doesn't put a small coloured dot next to file icons to mark files that have already been backed up or are ready to be sent. Archived files are available for recovery for up to a month after they've been deleted, a disappointingly short time limit compared to CrashPlan's never-delete policy. And there is no way to share your files.

Another negative is that Backblaze colocates its servers at a single data centre in the US where the service keeps redundant copies of all backups, thereby placing all of your backup eggs in one basket.

On the positive side, Backblaze has an unusual security system that uses a 2,048-bit RSA Public/Private encryption key to secure a 128-bit key that encrypts the actual files. It's the most airtight security of the five applications reviewed here.

Other nice features include an upload speedometer that shows how fast data moved during the last backup and a tool that helps you find a lost or stolen computer by notifying the user of its location if it is logged on to the Internet (although Backblaze can't disable the computer remotely).

Test results

In tests using Backblaze's default settings, the service's archived 978MB of data in 1 hour, 42 minutes and 32 seconds (note: Because each application's default settings differed, the amount of data each archived at this point differed widely).

A 25MB incremental backup took 4 minutes and 31 seconds, roughly halfway between CrashPlan's 1 minute and 3 seconds and Norton's 7 minutes and 23 seconds.

Searching for a lost file took Backblaze 2.1 seconds, about the same time as the others. I was able to resurrect the file in a quick 25.3 seconds, the fastest of the bunch.

Rather than restoring files online, Backblaze will send a hard drive or a set of DVDs containing your backups. This goes beyond Carbonite's Home Premium offer to send you a data-filled hard drive.

Backblaze has a two week free trial. The service costs a reasonable $50 (£30) a year for unlimited storage, but extra computers cost $5 each to back up, something that Norton doesn't charge for. Backblaze offers client software for PCs and Macs, but not Linux computers, and unlike the others, the service doesn't have any companion smartphone apps.

OUR VERDICT

All told, Backblaze can prevent a data disaster by protecting your most precious digital possessions, but it too severely limits what can be backed up.