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-   -   Feature Idea: disable Time Machine during backups (http://www.shirt-pocket.com/forums/showthread.php?t=5803)

RobLewis 09-30-2009 05:52 PM

Feature Idea: disable Time Machine during backups
 
I don't know if this is even possible, but it seems like it would be good if SD could temporarily suspend Time Machine backups while it was imaging a drive. I know you already suspend Spotlight indexing; this is sort of the same idea.

dnanian 09-30-2009 06:23 PM

There's no supported way of doing that, Rob.

tuni 09-30-2009 09:17 PM

Rob,
I turn Time Machine switch (system Preferences) to "off" prior to running SD. I know Dave said its not necessary,however, I don't see the harm in it and don't want to copy TM backups to my SD external drive. Takes too darn much space.

MacCetera 10-04-2009 02:13 PM

Scripts to stop and start time machine backups
 
Quote:

Originally Posted by RobLewis (Post 27207)
I don't know if this is even possible, but it seems like it would be good if SD could temporarily suspend Time Machine backups while it was imaging a drive. I know you already suspend Spotlight indexing; this is sort of the same idea.

I clone my 1TB TM drive nightly to another 1TB drive. I've got two shell scripts that I set in SD to run as pre and post backup scripts:

The first I named tm_disable.sh which contains only this line of code:
Code:

defaults write /Library/Preferences/com.apple.TimeMachine "AutoBackup" -boolean no
...and the other is tm_enable.sh with this line:
Code:

defaults write /Library/Preferences/com.apple.TimeMachine "AutoBackup" -boolean yes
It works with 10.5 and 10.6... I put the scripts in a directory on my source TM volume - and they get backed up too :)

-- Marc

KevinP 12-08-2009 01:47 PM

Disable Time Machine -- Not just a matter of optimization
 
Rob's original feature suggestion seems to be based on optimization -- preventing Time Machine and SuperDuper! fighting over resources, but I have discovered what seems to me a more important reason to consider this suggestion.

I occasionally boot from my SuperDuper! copy to make sure it's all right (hopefully everyone does this). The last time I did I was called away for a couple of hours. When I got back I found that Time Machine was complaining that it couldn't complete a backup. In my absence it had tried to make a Time Machine backup of my backup system on the same Time Machine drive I normally use. As there wasn't sufficient space for a complete second system on that disk, it started systematically deleting my old Time Machine backups, giving up only when there was only one left! Many month's worth of incremental Time Machine backups were deleted. As far as I can see, exactly the same thing could happen when using SuperDuper's Sandbox features.

Dave is right to note that there is no supported way to control Time Machine but Marc's idea of turning off Time machine through its preference file would at least ensure that any backup system had Time Machine initially disabled. Though this can be done by the user as Marc has done, I believe it is something that SuperDuper! should do by itself.

dnanian 12-08-2009 02:29 PM

If you tell Time Machine to not delete backups without notifying you, I don't think this particular situation can occur, Kevin (and that's the default, and fully supported by Time Machine).

We're really careful about only using supported interfaces in SuperDuper. Messing about with TM's undocumented preferences is just not something I'm willing to do.

KevinP 12-08-2009 06:05 PM

Unfortunately Dave, this is no longer true.

In Leopard, TM used to offer to warn before deleting backups. In Snow Leopard they changed this to: "Notify after old backups are deleted" (my emphasis). There are messages about this change all over the place.

Now I know it's not really your job to fix all the problems that Apple's created but, as a user, just checking the box as you suggested is not really an option any more.

By the way, I see that there's another thread started by Rob that more closely matches this topic (though your response was the same).

dnanian 12-08-2009 06:11 PM

Well, that's a silly change, but out of my control, of course.

When Apple documents a method of controlling Time Machine, I'll consider supporting it. Until that time, the script commands above (which are not supported by me) will work for users this may impact... but it's generally unnecessary as a means of controlling I/O, as you indicated.

RobLewis 12-08-2009 06:16 PM

FWIW, I've been using the "defaults write" command in pre- and post-backup scripts for several weeks now, with no apparent problems.

dnanian 12-08-2009 06:26 PM

I'm not suggesting you're definitely going to have problems, only that I don't want to use undocumented preferences to control things, especially in a situation where it's non-essential.


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