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From: Jason S on 1 Jun 2010 08:57
I have Time Machine set up on my MacBook Pro. Every now and then when
it backs up, it'll back up several gigabytes of information, even
though I haven't touched my computer in a day or two. I have no idea
what new information it could be backing up that is so large. Most of
the time, it happens when nothing has even been modified on the
computer. Any idea what could be causing this?

--
Jason

From: David Empson on 1 Jun 2010 09:55
Jason S <jasonsavlov(a)me.com> wrote:

> I have Time Machine set up on my MacBook Pro. Every now and then when
> it backs up, it'll back up several gigabytes of information, even
> though I haven't touched my computer in a day or two. I have no idea
> what new information it could be backing up that is so large. Most of
> the time, it happens when nothing has even been modified on the
> computer. Any idea what could be causing this?

I can think of three potential explanations:

1. Entourage

If you are using Entourage for e-mail, and it has a multi-gigabyte
database, and you haven't excluded it from Time Machine backups, then
receiving a single e-mail message (or possibly just running Entourage)
will trigger a new backup of the entire e-mail database.

2. Virtual machines

If you have any virtual machine software (e.g. VMware Fusion, Parallels
Desktop or VirtualBox) and it is using a virtual disk image as a file,
and it was set up as a single huge file rather than a sparse bundle, and
it isn't excluded from the Time Machine backup, then starting up the
virtual machine will modify its disk image, which will need to be backed
up again in its entirety.

3. FileVault

If any user account on your computer is using FileVault, especially if
the account existed on Mac OS X 10.4 and the computer was subsequently
upgraded to Leopard or Snow Leopard, the encrypted disk image holding
the entire home folder will need to be backed up by Time Machine after
the user logs out. Simply logging in as that user is probably sufficient
to change _something_ in the encrypted disk image, and this would
certainly happen if you ran any application which resaved its
preferences file on quit (as many do).

If it isn't one of those three obvious candidates, you'll need some way
to find out what has changed between consecutive Time Machine backups.

This one (graphical but rather raw) is one possible solution:

<http://www.charlessoft.com/TimeTracker.zip>

See general notes on <http://www.charlessoft.com>


This article on Mac OS X Hints also has a reference to a command line
script called timedog which does the same sort of task:

<http://www.macosxhints.com/article.php?story=20080714124323976>

--
David Empson
dempson(a)actrix.gen.nz
From: Jason S on 1 Jun 2010 11:50
On 2010-06-01 09:55:29 -0400, David Empson said:

> Jason S <jasonsavlov(a)me.com> wrote:
>
>> I have Time Machine set up on my MacBook Pro. Every now and then when
>> it backs up, it'll back up several gigabytes of information, even
>> though I haven't touched my computer in a day or two. I have no idea
>> what new information it could be backing up that is so large. Most of
>> the time, it happens when nothing has even been modified on the
>> computer. Any idea what could be causing this?
>
> I can think of three potential explanations:
>
> 1. Entourage
>
> If you are using Entourage for e-mail, and it has a multi-gigabyte
> database, and you haven't excluded it from Time Machine backups, then
> receiving a single e-mail message (or possibly just running Entourage)
> will trigger a new backup of the entire e-mail database.
>
> 2. Virtual machines
>
> If you have any virtual machine software (e.g. VMware Fusion, Parallels
> Desktop or VirtualBox) and it is using a virtual disk image as a file,
> and it was set up as a single huge file rather than a sparse bundle, and
> it isn't excluded from the Time Machine backup, then starting up the
> virtual machine will modify its disk image, which will need to be backed
> up again in its entirety.
>
> 3. FileVault
>
> If any user account on your computer is using FileVault, especially if
> the account existed on Mac OS X 10.4 and the computer was subsequently
> upgraded to Leopard or Snow Leopard, the encrypted disk image holding
> the entire home folder will need to be backed up by Time Machine after
> the user logs out. Simply logging in as that user is probably sufficient
> to change _something_ in the encrypted disk image, and this would
> certainly happen if you ran any application which resaved its
> preferences file on quit (as many do).
>
> If it isn't one of those three obvious candidates, you'll need some way
> to find out what has changed between consecutive Time Machine backups.
>
> This one (graphical but rather raw) is one possible solution:
>
> <http://www.charlessoft.com/TimeTracker.zip>
>
> See general notes on <http://www.charlessoft.com>
>
>
> This article on Mac OS X Hints also has a reference to a command line
> script called timedog which does the same sort of task:
>
> <http://www.macosxhints.com/article.php?story=20080714124323976>

I don't use any of the three possible causes you mentioned, so I'm
going to try one of the other two diagnostic solutions you recommended
next time it happens. It hasn't happened in a few days, but it'll
probably start up again like always. Thank you for your help!

--
Jason

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