Thoughts on the Time Capsule

On February 22, 2011, in Recommendations, Technology Horror Stories, by Rob Levandowski

A few years back, I bought an Apple Time Capsule.  I had just purchased a new iMac to replace my Power Macintosh G5.  The G5 had two internal drives, allowing me to use Time Machine (Apple’s automatic incremental backup/snapshot system) on the second drive.  As the iMac has no provision for a second internal drive, my choices were to attach an external drive, or go for the Time Capsule.  I bought the Time Capsule, thinking it would be more useful: it could also back up a few other Macs in the house.

I just bought a newer iMac, and I bought a FireWire external disk for it and migrated my backups.  It’s time to bury the Time Capsule.

First, I should say I didn’t have any problems with the Time Capsule’s reliability—unlike, apparently, a great many people.  It seems that early builds of the Time Capsule were prone to premature failure.

No, it’s the actual usability of the thing that soured me.

The Time Capsule is essentially a wireless access point with an integrated network-accessable storage (NAS) device.  Time Machine is picky; it won’t play nice with many other NAS devices.  However, it doesn’t seem to be a particularly fast NAS device.

My iMac was connected via a Gigabit Ethernet network. While I can copy files Mac to Mac over my GigE network at essentially the limits of the hard drives’ speeds, the Time Capsule is a laggard. It seems like it has an underpowered processor. That wouldn’t be surprising, except that Apple commands a premium price for the device, and Apple now has their very own powerful embedded processor chip, the A4.

The poor network performance pales, however, compared to the way Apple chose to implement Time Machine for networked volumes.

On a system with a directly-attached hard drive for Time Machine, Mac OS X uses features of the HFS+ filesystem to work the backup magic. These features aren’t available to network-mounted volumes.  To work around this, Time Machine creates a disk image file on the Time Capsule in a “sparse bundle” format that can grow and be modified as backups are made.

It takes forever for the system to parse in the disk image. Even with a dual 3.06GHz Core 2 Duo.  Even with a quad-core Core i7. If you’ve changed a lot of files, your hourly backup may take more than an hour.  During that time, your system can be sluggish as it deals with the backups.

But that’s nothing compared to trying to restore a file.

With a directly-attached drive, Time Machine is wonderfully responsive.  You can fly back through time, find your file, and restore it in short order.

With a Time Capsule, you’re going to need a lot of patience.  You’ll click on the Time Machine icon… and wait.  Eventually, you may get a progress bar telling you that it’s working on mounting the backup image.  You’ll wait another minute or two.  Finally, the Time Machine screen will appear.  Twenty or forty seconds after that, the contents of the directory you want to restore may actually show up on that screen.  When you click to go further back than the most recent backup… prepare for lag.  The further you go back, the longer the wait.  Uncharacteristically for Apple, there’s no feedback to reassure you that the system is doing something with all these pauses; if you aren’t within sight of your Ethernet switch to notice the blinking lights, you might think the system has frozen.

Did I mention that it’s even slower if more than one computer is trying to read or write to it at a time?

With the Time Capsule, you have to be truly committed to restoring a file to put up with the delays.

The really crazy part came when I tried to delete the sparsebundle file after using Disk Utility to restore its contents onto my new FireWire drive.  After the Finder warned me that the file would be deleted immediately, and I clicked OK, it took about an hour for it to delete the one file.  (That’s probably because it’s a bundle hiding who knows how many actual files behind one icon.)

It does work, if agonizingly slowly, and it has saved us from disaster once: my girlfriend’s hard drive died, but we were able to restore its contents from the Time Machine backup on the Time Capsule.  Of course, it took the better part of a day to restore under 200GB of data, but she was happy to get her stuff back.

One place where the Time Capsule does fall down is in certain migrations from one Mac to another.  The files on the Time Capsule are keyed to the system’s name and MAC address.  When you move to a new Mac, you may find you have to create a new backup file on the Time Capsule.  While you can still access the old file, Time Machine will no longer automatically prune that file when your backups fill the Time Capsule.  You’ll either have to delete your old backup image, accept a much smaller active backup space, or attach an external USB2.0 drive to the Time Capsule for additional storage.  In my case, I used Disk Utility to “restore” the old image onto a new external hard drive.  When I pointed Time Machine at the external hard drive, it recognized that it contained backups for a Mac with a different name, and asked if I wanted to use it anyway. You don’t get this option if all you have is the Time Capsule.

I hope Apple creates a Time Capsule Version 2 that’s actually useful for backing up and restoring multiple Macs in one household. I’d like to see a version that has two or three 2.5-inch, 10k RPM drives with a hardware RAID, and an A4 processor providing wire-speed networking. It should also implement a network protocol that works natively with Time Machine, not using the wonky sparsebundle format and its speed flaws. (However, it should have some way to dump any given machine’s backups to a disk image, so that users can migrate.

In the meantime, my advice to Mac users is: if at all feasible, go buy external FireWire 800 or USB2.0 hard drives for each of your Macs, and use that as your Time Machine setup.  It will be faster, it will be easier to deal with, and you’ll get more use out of them.  External hard drives are cheap nowadays.


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