10.6.3 Resizing Sparsebundle Disk Images

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10.6.3 Resizing Sparsebundle Disk Images

Hi All,
I just updated to OSX 10.6.3 and am noticing a strange issue. First off I am using an unsupported NAS device for my Time Machine backups, however I have actually seen the box (Promise NS4600) sold at Apple Stores. Anyhow I have several Macs backing up to this NAS. Before 10.6.3 I had set a maximum size that the sparsebundle could grow to for each of the sparsebundle images. The problem is that when running time machine, it appears that if the sparsebundle is not the same size as the volume, the system automatically resizes the sparsebundle.

com.apple.backupd[1575]: Resizing backup disk image from 476.8 GB to 2743.0 GB

This is definitely not what I want. Does anyone know a workaround/fix? Is there a plist file I can edit where I can tell time machine not to resize my sparsebundle? Any ideas? Thanks.

Mac OS X (10.6.3)

Posted on Mar 31, 2010 8:42 AM

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Answer 1

Mar 31, 2010 12:40 PM in response to skerb1

skerb1 wrote:
the system automatically resizes the sparsebundle.

com.apple.backupd[1575]: Resizing backup disk image from 476.8 GB to 2743.0 GB

That was mentioned yesterday in this thread:

http://discussions.apple.com/message.jspa?messageID=11292518

This is definitely not what I want.

Why are you concerned? If it's because you want space on the same volume reserved for non-Time Machine use, that might be better accomplished by creating a separate volume.

Does anyone know a workaround/fix? Is there a plist file I can edit where I can tell time machine not to resize my sparsebundle?

I haven't heard of anyone mentioning such a thing.

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Answer 2

Pondini

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Mar 31, 2010 4:15 PM in response to William-Boyd-Jr

William Boyd, Jr. wrote:
. . .
That was mentioned yesterday in this thread:

http://discussions.apple.com/message.jspa?messageID=11292518

This is definitely not what I want.

In that thread, the poster said it was a one-time thing; it happened on the first backup after the upgrade, but not subsequently. It appears that if you re-size them after that first backup, they'll be left alone thereafter (at least until the next upgrade, perhaps).

Or have you done that, and subsequent backups are resizing it again?

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Answer 3

Mar 31, 2010 4:48 PM in response to Pondini

Pondini wrote:
In that thread, the poster said it was a one-time thing; it happened on the first backup after the upgrade, but not subsequently. It appears that if you re-size them after that first backup, they'll be left alone thereafter (at least until the next upgrade, perhaps).

Or have you done that, and subsequent backups are resizing it again?

I'm not the OP. I'm still running OS X 10.5, so that's not something I'd have experienced.

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Answer 4

Pondini

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Mar 31, 2010 7:18 PM in response to William-Boyd-Jr

Sorry, I meant to address that to skerb1.

skerb1: Can you confirm whether it's a one-time thing (if you resize a sparse bundle and do another backup, does TM resize it back again)?

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Answer 5

skerb1 Author

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Mar 31, 2010 8:52 PM in response to William-Boyd-Jr

William Boyd, Jr. wrote:

Why are you concerned? If it's because you want space on the same volume reserved for non-Time Machine use, that might be better accomplished by creating a separate volume.

As far as I know, this is not possible on the NS4600 in a RAID5 configuration.

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Answer 6

skerb1 Author

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Mar 31, 2010 9:02 PM in response to Pondini

Pondini wrote:
skerb1: Can you confirm whether it's a one-time thing (if you resize a sparse bundle and do another backup, does TM resize it back again)?

I am not sure. When trying to resize the sparsebundle (as root) I was getting permission denied error (EPERM):

hdiutil resize -size 300g xyz_1122aabbccdd.sparsebundle

This is perhaps due to the restrictions that Promise puts on the NS4600? I may have to copy the sparsebundle over to my machine, resize it, and put it back on the NAS...ugh...

Message was edited by: skerb1

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Answer 7

Apr 6, 2010 7:17 AM in response to skerb1

I am using a Drobo connected to a Mac Mini Server. I use the Drobo for both TM backup and remote storage. I backup three Macs and the sized sparsebundle solution has always worked well up to the 10.6.3 upgrade. I am also keen to see if anyone has a solution.

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Answer 8

Pondini

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Apr 6, 2010 8:00 AM in response to Mike Turner

I'll ask you the same question: once you've installed 10.6.3, then re-sized the sparse bundle to be smaller than the size of the volume, when you do new backups, does that smaller size remain, or does it get re-set to the size of the volume again?

If not, can you partition the Drobo? (I've seen conflicting posts on whether that's possible.)

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Answer 9

Apr 6, 2010 11:41 AM in response to Pondini

The sparsebundle was set to 750GB. TM then resized it to 8TB which is the virtual maximum for the Drobo. The actual disk space available is 1.8TB (3 x 1TB).

"Resizing backup disk image from 750.0 GB to 8191.6 GB"

It is possible to re-partition the Drobo however the point is that sparsebundles have been set up for each device so that they will fill to that maximum and then TM will recycle the space within the sparsebundle. This has been working up to 10.6.3. I have an iMac G5 on 10.5.8 and that is still working fine.

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Answer 10

Pondini

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Apr 6, 2010 11:54 AM in response to Mike Turner

Mike Turner wrote:
The sparsebundle was set to 750GB. TM then resized it to 8TB which is the virtual maximum for the Drobo. The actual disk space available is 1.8TB (3 x 1TB).

"Resizing backup disk image from 750.0 GB to 8191.6 GB"

Yes, I understand that the first backup after the 10.6.3 update did that.

My question is, if you reduce it and run another backup, does it stay reduced, or will the next backup expand it again?

Since you can partition the Drobo, that's a workaround, if the sparse bundles won't stay at the reduced size.

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Answer 11

Apr 6, 2010 12:11 PM in response to Pondini

Pondini wrote:
Since you can partition the Drobo, that's a workaround, if the sparse bundles won't stay at the reduced size.

Since the Drobo seems to have a "virtual size" quite a bit larger than the actual size, that resizing based in the virtual size might eventually cause trouble.

Just curious: Is there a way to interrogate a "sparsebundle" file to learn its declared maximum size? I tried to make hdiutil do that but didn't have any luck. Finder "Get Info" didn't seem to show it either.

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Answer 12

Pondini

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Apr 6, 2010 12:22 PM in response to William-Boyd-Jr

William Boyd, Jr. wrote:
. . .
Just curious: Is there a way to interrogate a "sparsebundle" file to learn its declared maximum size? I tried to make hdiutil do that but didn't have any luck. Finder "Get Info" didn't seem to show it either.

Yes. Disk Utility. Oddly enough, it won't work while the Disk Image is actually mounted, but click +Images > Resize+ in the menubar, then locate it, and it will show the max size.

In some cases, you can then re-size it (but I can't get it to actually re-size one on my USB drive connected to my Airport, or one in my home folder), although sometimes the log said it did. Note that you have to click +Window > Show Log+ in the menubar to see the messages.

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Answer 13

Apr 6, 2010 1:56 PM in response to Pondini

Pondini wrote:
Yes. Disk Utility. Oddly enough, it won't work while the Disk Image is actually mounted, but click +Images > Resize+ in the menubar, then locate it, and it will show the max size.

Thanks for the info.

In some cases, you can then re-size it (but I can't get it to actually re-size one on my USB drive connected to my Airport, or one in my home folder), although sometimes the log said it did. Note that you have to click +Window > Show Log+ in the menubar to see the messages.

That's another thing I didn't know about. Thanks again.

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Answer 14

Apr 6, 2010 4:49 PM in response to Pondini

Sparsebundle was resized to the useful maximum (for test purposes 150GB) using hdiutil. The next TM backup then resized it back to 8TB. This is repeatable.
Disk Util will only show the used data size. To see the maximum size, right click on the sparsebundle, Show Package Contents, open Info.plist. Size is the last number in bytes.
Repartitioning is not a practical workaround for me, I would rather revert to 10.6.2. There is not an issue at the moment as none of the TM backups will exceed the capacity for months, but it would be interesting to see what has changed since 10.6.2 and if there is a fix.

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Answer 15

Pondini

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Apr 6, 2010 4:54 PM in response to Mike Turner

Mike Turner wrote:
Sparsebundle was resized to the useful maximum (for test purposes 150GB) using hdiutil. The next TM backup then resized it back to 8TB. This is repeatable.

Rats. That's not good news, but at least we know it. Thanks for the confirmation.

If you have AppleCare, it might be worth a try calling them and reporting it as a bug.

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