Backup roundup (part 2) - Mozy on Mac and Windows

Mozy was the first online backup service I tried using seriously. The pricing seemed attractive – around $300 for three machines for two years, without storage limits – as did the Mac support.

My first impressions were positive: a relatively simple setup process, picking the directories to back up, then leaving the client to upload the data to their servers. Ultimately, I wanted my Mac home directory backed up excluding my Parallels virtual machine – at 40 Gb, this would take quite a few days, so I enabled backups a few Gb at a time until I had the selection I wanted). The Windows directory structure was a little more complex, but not difficult to accommodate within Mozy: after a few days, both my Vista and XP systems were backed up as well. The presence of a second drive where most of my data lived didn’t cause any issues either.

Internally, the backup algorithm appears to be based on RDiff deltas, tracking file status in an SQLite database. That should enable delta compression, uploading only the changed parts of each file after the initial backup. Running a backup consists of “offering” the server batches of files – up to 500 at a time, it seems – which could be deletions, new files or new versions of existing files. The server then asks for any necessary data to be uploaded, after which the client moves on to the next batch.

A nice, sane design, but I have encountered several problems in actual usage. On Windows XP, at some point something became corrupted; the best solution Mozy could come up with was to uninstall, delete some leftover files manually then reinstall, which is irritating, particularly since this resulted in having to reconfigure Mozy then re-process every file in the backup set.

I hit two other irritating glitches in the Mac version: early in 2009 the file state database appeared to become corrupted, so Mozy began the multi-day process of rebuilding it. A few months earlier, it stopped obeying the path exclusions I had set (essentially, my whole home directory minus my Parallels virtual machine) – and started trying to upload my entire 30 Gb virtual hard drive. Once a file has been backed up, Mozy only sends the changes – but there is no support for resuming a partial transfer. As a result, every attempt to upload that 30 Gb virtual drive failed part-way, then started again from scratch the next time. The Mozy support response was not to use exclusions, but to add only the folders I wanted backed up in their entirety.

The most serious issue, however, came when I performed a fairly large restore operation. Trying to restore around 13 Gb of data (photographs from my recent vacation in Boston and New York, in RAW format) ran overnight — then informed me at the end that “some” files had not been restored. Three of them, apparently, but the logs gave no indication which files had been missed or why!

The user interface is also quite limited and crude compared to Time Machine and Carbonite, although the Windows version recently started adding status icons to files in Explorer in the same way Carbonite does.

One significant advantage with Mozy comes in the web interface. Where Carbonite is built around an elaborate client package which handles everything, Mozy allows you to download backed up data from their website, wherever you are; Carbonite does not. This proved useful when I needed to access some data on my home system from elsewhere, and would also be very helpful in a disaster recovery situation (where the backed up system is unavailable) when you need urgent access to a particular part of the data: Carbonite requires you to install the client software, rather than just logging in to the website. Mozy also allows you to order, for a charge, copies of your data on optical media — with a reasonable Internet connection, though, you would have to be restoring several tens of gigabytes for this to be faster than the free option of restoring online.

Overall, the product is a good one, with some irritating glitches and rough edges. It is slowly improving; my only serious concern is the problem I encountered with a large file restore apparently missing a few files without detail or explanation. Barring significant improvements, though, I will be switching my two Windows systems from Mozy to Carbonite once the two years are up. Carbonite apparently have a Mac version in beta at present, with release scheduled early this year: I’m looking forward to comparing the two Mac versions when that happens.

Features and advantages

Limitations and problems


For Mac users, Mozy is a good choice, giving cost-effective off-site backup with a fairly trouble-free user experience, although not reliable enough to trust as a sole backup — best used as a fallback in the event Time Machine can’t help. For Windows, Carbonite is the better choice.

Subscribe via FeedBurner Add to Technorati Favorites

blog comments powered by Disqus