Time Capsule: Using TimeMachineEditor to decrease the frequency of Time Machine backups

Posted by Pierre Igot in: Macintosh
June 12th, 2008 • 3:33 pm

Following my recent misadventures with a damaged Time Capsule backup disk image causing repeated kernel panics, and some reader feedback about the issue, I downloaded a small third-party utility called TimeMachineEditor.

It is a simple application whose sole purpose is to enable you to customize the schedule of Time Machine backups.

I have reasons to suspect that the damaged disk image on the Time Capsule was caused by the fact that I abruptly interrupted a TM backup in progress by closing my wife’s laptop while the screen was asleep.

A Betalogue reader suggested via e-mail that he didn’t think that any program could handle such a situation gracefully, whether it’s Time Machine or a third-party backup utility such as Retrospect.

My response to this is that, from the user’s perspective, it’s an unacceptable limitation of the backup software. There is simply no way that the user of a Mac laptop should also be expected to always make sure that there is no TM backup in progress before closing his machine.

The whole point of having a reliable backup setup is that you don’t even have to think about it. A limitation of the system that forces you to constantly remember to double-check before you do something as simple as closing your laptop directly breaks this fundamental requirement of a good backup system.

If there are engineering limitations that make it difficult for a backup system to handle such a situation gracefully—and indeed, that can so easily cause disk image corruption and catastrophic kernel panics—then these engineering limitations need to be urgently eliminated. Engineering is at the service of usability.

That said, until Apple fixes this problem and eliminates the risk of users inadvertently damaging Time Machine disk images (with such disastrous consequences), I need to be pragmatic and find a solution.

In my view, reducing the frequency of Time Machine backups is a easy way to significantly reduce the risk of damaging the disk image. I really do think that hourly backups are overkill, especially for someone like my wife. Sadly, there is nothing in the Time Machine user interface that lets you adjust the frequency of backups.

But apparently this TimeMachineEditor application can change the backup interval by simply “updat[ing] a system configuration file.” Presumably this means that Time Machine’s internals do include options for adjusting the schedule, but that these options simply aren’t accessible to the end user through the user interface.

So I installed the utility this morning and used it to change the schedule to a single daily backup at 3:00 pm. As the TimeMachineEditor instructions indicate, the change is not reflected in the Time Machine preference pane, which still states that backups will take place hourly, and which now gives a wrong time for the next scheduled backup. But regardless of what the preference pane says, it does appear that the change works, and my wife’s laptop has only run its Time Machine backup once today, exactly at 3:00 pm.

So it looks like the utility works. I still had to explain to my wife that, in order to avoid problems with the Time Capsule in the future, from now on she should make sure that, if she needs to close the laptop around 3:00 pm, she should always make sure that no backup is in progress. But it’s much better than having to remember to check this all the time, all through the day.

It’s not an ideal solution, but it’s probably an acceptable compromise until the engineers get their act together. It certainly should greatly reduce the risk of another incident of irreparable disk image damage on the Time Capsule—at least I hope so!

3 Responses to “Time Capsule: Using TimeMachineEditor to decrease the frequency of Time Machine backups”

  1. ThiH. says:

    You write:
    “I have reasons to suspect that the damaged disk image on the Time Capsule was caused by the fact that I abruptly interrupted a TM backup in progress by closing my wife’s laptop while the screen was asleep.”

    Actually, that does not (or should not) cause a corrupted backup. I have two mac laptops and one Time Capsule and all the time I randomly stop a backup by closing the laptop when I need to leave. That hasn’t caused any backup corruptions. I’ve owned the Time Capsule for at least 2 months now.

  2. rodneyw says:

    G’day Pierre,

    I found your blog via rixstep. I like the way that you think!

    With regard to this issue – it bothers me that OS X has a kernel panic over a corrupted disk image at all! Why should there be a panic simply because a non-system disk is corrupted? Why have a “verify disk image” option if you can’t even do something with it?

    I like the fact that OS X needs rebooting a lot less than any form of Windows that I have ever used. But why shouldn’t an Operating System be able to detect that there is a problem and handle it elegantly?

  3. ssp says:

    Sending the machine to sleep should not corrupt anything no matter what. The compuer knows it will go to sleep and applications get the opportunity to adjust to that (look at iTunes which stops playing compared to audio streams in web pages via Flash which don’t).

    If there’s anything problematic about backups to a Time Capsule it should be that you lose power or your wireless network breaks down. And, frankly, if Apple didn’t make Time Capsule to handle those situations well, they simply failed at their job.

    I’d say that corrupted disk images and kernel panics by trying to use them point in a single direction: a buggy OS.

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