In "Take Control of Upgrading to Leopard [1]," I spent a few pages talking about how to turn on and configure Time Machine, but I didn't go into much detail because I already have another book, "Take Control of Mac OS X Backups [2]," which is all about backups and is therefore the proper place to put a full explanation of if, when, why, and how to use Leopard's new built-in backup feature. I am at this very moment working hard on a new version of that book that will tell you everything you want to know about Time Machine, and though I can't project an exact release date yet, we will certainly make it available as soon as we possibly can.

However, my work on the new book has been slowed down considerably by having to take time out, on at least a dozen occasions in the last few days, to answer email messages about what I think of Time Machine, how well or poorly it accomplishes some task, whether it's appropriate for enterprise backups or a suitable replacement for Retrospect, and so on. (The messages usually start, "I know you're probably going to cover this in an update to your backups book, but...") I am, of course, always happy to answer messages from readers, but I never dreamed Time Machine would turn into such a drain on my productivity! So, in the interest of heading off more inquiries for a few more days so that I can actually get the book finished, I'd like to take a moment here to offer my initial impressions of, and suggestions regarding, Time Machine. For more information... wait for the book!

Out of Time -- First, some bad news. At the Worldwide Developers Conference in June 2007 - just four months ago - Steve Jobs announced that Time Machine would work with an AirPort Disk (a USB hard drive attached to an AirPort Extreme N base station). As recently as two weeks ago, the same claim appeared on the Time Machine page on Apple's Web site. But then it mysteriously disappeared, and sure enough, the shipping version of Leopard offers no support for AirPort Disks. For whatever reason, presumably technical difficulties of some sort, Apple dropped that feature at the last minute. So, while it's still possible to back up multiple Macs in your home or office over a network, even wirelessly, doing so requires a host Mac (running Leopard or Leopard Server) - a step backward in convenience. The same limitation applies to NAS (network-attached storage) devices from other vendors. Although it may be possible to work around this problem [3], I wouldn't trust my backups to an unsupported hack, and I strongly discourage you from doing so as well.

That's not the only missing feature. Apple had previously claimed that Time Machine would support encryption, but it doesn't. It does keep FileVault archives encrypted, but the cost of doing so is not being able to back them up until you're logged out of your account - a significant inconvenience. Yet another missing feature is the capability to specify a time limit beyond which older files will be deleted from your backup disk; now Time Machine simply keeps going until it nearly fills up your disk, and then starts purging older files - with an optional warning, but without an option to offload those older files to other media for long-term storage.

Apart from things many of us expected because Apple had told us about them, Time Machine lacks numerous important features common in other backup programs. A biggie: it can't make bootable duplicates; if your hard drive dies, you'll spend long hours restoring your Time Machine backup to a new drive before you can get back to work. It doesn't let you schedule times when it won't run, though you can manually turn it on and off whenever you want. You can't specify more than one destination disk and switch between them automatically (as you might want to do, for example, to keep an extra backup offsite - something I recommend). (It is possible to work around this in various ways, but I have to do more experimentation before I can provide reliable advice.) You can't back up to an iDisk or to optical media. You can't compress your backups - you're going to need, at a bare minimum, free disk space 1.2 times the size of the data you want to back up. And although you can manually specify files, folders, or volumes to be excluded from your backups, Time Machine offers no intelligent filtering (for example, excluding all disk images or all downloaded videos).

Go Forward to Go Back -- I started with the bad news not to diss Time Machine or persuade you that you shouldn't use it, but to put it in perspective. It's the very first version of a brand-new technology. It has limits and bugs (such as a problem with Aperture - see "Leopard Early Fixes and Warnings [4]"), and seemingly lost some features just before its initial release. So despite the one-click setup (very nice) and the groovy 3-D interface for restoring files (extra super nice), it is not the Ultimate Mac Backup Program. At least, not yet.

On the other hand, I can think of at least one excellent reason you might want to start using Time Machine right now: it's guaranteed to be compatible with Leopard! Some of your existing backup software may not be. For example, the developers of SuperDuper [5] are working hard on a Leopard update, but it's not quite there yet. EMC has announced that a Leopard compatibility update for Retrospect [6] will be available within 30 days, and Prosoft says that they're preparing an update to Data Backup 3 [7]. Among the backup software already working under Leopard is CrashPlan [8], thanks to an update on 27-Oct-07. A new version of Carbon Copy Cloner [9] released last week appears to work with Leopard, but may have a few glitches left. And Apple's own Backup [10] just had a minor update for Leopard compatibility (among other things). If you're using any of the dozens of other backup utilities out there, check with the developer for information on its support for Leopard.

Time Machine Impressions -- I've been using the final version of Leopard on my main Mac for the past few days, and based on what I've seen so far, Time Machine appears to work approximately as advertised. It does back up and restore files correctly when I ask it to. However, a few things are not quite as I expected:

• Hourly backups, even to a fast external hard drive with a FireWire 800 interface, often take as long as a half hour! So basically, Time Machine is actively copying files at least half the time. Why does it take so long? It appears that several factors are involved. First, I have .Mac Sync turned on, which results in quite a few files being modified (and therefore, marked as needing backup) every time it runs, whether manually or on a schedule. Ditto for iDisk Sync - since I have a local copy of my iDisk, every time I modify a file there, Time Machine wants to back up that (very large) disk image again. Also, I have Mail checking six IMAP accounts, and every time I get new mail, not only the messages themselves but also Mail's envelope index file and junk mail filter statistics are updated. A number of other background processes on my machine also change files fairly frequently. The net result: on my Mac, Time Machine backs up tens of thousands of files, totaling hundreds of megabytes, every single hour.
• Disk images are a bit of a problem. If you use Parallels Desktop or VMware Fusion, you probably have a very large disk image to hold your Windows installation. Every time you change even a tiny file in Windows, Time Machine is obliged to back up that entire huge file again. The same goes for PGPdisk or even an encrypted disk image you create with Disk Utility to hold confidential files: any small change marks the entire large file as needing to be backed up again. This results in a tremendous waste of space on your backup disk, not to mention a longer time spent performing each backup. Several newer backup programs, including CrashPlan and QRecall [11], can back up just the changed portion of a large file, but Time Machine's approach makes doing so fundamentally impossible.
• If I activate Time Machine while in Mail, I immediately see dozens of spam messages in my Inbox that were never there before! Mail's junk mail filter intercepted them as soon as they arrived and routed them to my Junk mailbox, but apparently Time Machine doesn't care; Junk is, in fact, the only mailbox that's dimmed when in Time Machine's restore mode, so I can't look at how just that one folder was in the past. I think Apple is trying to be helpful here by highlighting the fact that a "missing" email message may not be missing at all but merely mistakenly filed in your Junk mailbox. But I don't want Time Machine to second-guess me like that.
• Third-party support for Time Machine is still lacking. It's great that I can restore individual items from Mail, Address Book, iPhoto, and so on. But I'd like to restore individual keychain items from 1Password, individual snippets from DEVONthink Pro Office or Yojimbo, and individual records from FileMaker Pro databases. So far, very few non-Apple applications support Time Machine at the record level. If and when they do, Time Machine will become vastly more useful.

Ultimately, I expect I'll continue using Time Machine, but only as one part of a broader backup strategy. Time Machine is pretty good at what it does, and may get even better over time. Even in the best case, though, I'll need some other software to make bootable duplicates, an additional strategy to deal with offsite backups, and probably some fiddling to deal with problem areas like disk images and never-ending hourly backups. And now, if you don't mind, I must get back to my testing, so that I can explain exactly how to do all these things in that book I'm writing!

[1]: http://www.takecontrolbooks.com/leopard-upgrading.html?14@@!pt=TB902
[2]: http://www.takecontrolbooks.com/backup-macosx.html?14@@!pt=TB902
[3]: http://forums.macrumors.com/showthread.php?p=4402934
[4]: http://db.tidbits.com/article/9269
[5]: http://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html
[6]: http://www.emcinsignia.com/products/smb/retroformac/
[7]: http://www.prosofteng.com/products/data_backup_info.php
[8]: http://www.crashplan.com/
[9]: http://www.bombich.com/software/ccc.html
[10]: http://www.apple.com/support/downloads/backup312.html
[11]: http://www.qrecall.com/

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