Tue, 03 Nov 2009 Macworld Secrets: Online backup services

Backups work best when you have multiple copies, at least one of which is both up to date and offsite. OS X’s Time Machine feature – and the availability of high-capacity, low-cost hard drives – make it possible for you to back up regularly and rotate drives through backup sets, storing a full backup safely away from the source data.

But what about when the worst happens? When fire strikes, a lightning bolt fries your computers and backup drives, or a burglar makes off with the goods? A drive stored off-site helps – but the files stored on it are out of date the second you unplug it and haul it away. An online backup service could be the perfect addition to your backup plan.

With large amounts of storage available at a low cost or even for free, and with today’s fast internet connections, backing up your files online has become more viable. Online backup providers also add depth to your archives, since most of them store data in such a way that you can retrieve several – or even several hundred – previous versions of a modified file.

Here’s a look at seven services with Mac software for managing automated backups.

How they work
All the hosted backup services we looked at use Mac software to synchronise data on one or more of your computers with their hard drives and services elsewhere on the internet. All support OS X 10.4, 10.5, and 10.6 (all except for Carbonite, which supports just 10.4 and 10.5). All support Windows too, and some support Linux.

Your initial backup requires that you upload every byte of data. Only one service, CrashPlan Central, lets you jump-start that process by loading a drive it sends you with up to 1TB of data (although it’s currently only available in the US).

The services generally store your data on massive server farms that might have hundreds or thousands of terabytes of storage capacity; companies provide few details about where and how they store data. Jungle Disk is unique among the services we’ve looked at here in relying on cloud-based metered storage, offering a choice between parent company Rackspace, and Amazon’s Simple Storage Service (S3).

After the initial backup, all the services are cleverly efficient about sending changes. Rather than re-uploading a 10MB file – or even a 10KB one – the software on your computer breaks a file into pieces, and then creates a mathematical summary of each piece. The program compares the summary to what’s stored on the server and then transfers only changed or new pieces.

That process also allows you to reconstruct an older version of a file using a base file, with any subsequent changes patched on top, to reach the version you want. These piecemeal updates are also typically compressed to make the upload even faster.

Most of the services let you specify whether you’d prefer that deleted files be removed immediately from the backup set, or retained as part of stored older versions – either forever or for a certain number of days.

Every service has its limitations regarding how it finds, packages, encrypts, compresses, uploads, and receives changed files. When we tested each service on a cable internet connection that regularly tops 5Mbps upstream, each was able to store several gigabytes overnight.

With competitive pricing, easy-to-use Mac software, and access to multiple destinations integrated in one package, CrashPlan Central is a great option.

Pricing
Backup service providers follow one of two pricing schemes: flat-rate storage or per-gigabyte (metered) storage. Only Jungle Disk and SpiderOak are metered.

Flat-rate services charge a set rate per computer and include unlimited storage, while metered services allow an unlimited number of computers access to a pool of data. IDrive is an exception – it offers 150GB of storage for up to five computers for a flat monthly rate.

The flat-rate providers typically charge about $5 (£3) per computer on a monthly basis, although several allow advance payment for a year or more at a time, or offer a discounted annual option.