size limit of 16TiB to sparsebundle files?

Question

size limit of 16TiB to sparsebundle files?

I manage several servers with higher disk volumes. Some use OsX.

At one particular customer, the OsX 10.7.5 fileserver of has 21TB available and the OsX 10.8.4 backupserver has 25TB. Using TimeMachine we stumbled across an apparent size limit of 16TiB (17.59TB) for sparsebundle files. Whenever we try to expand the sparsebundle beyond that size, we receive error messages about exceeding `the´ size limit.

Which one? I found no information regarding such limitations. A sparsebundle is a virtual "Mac OS Extended" filesystem [partition in a virtual disk], which should be able to grow up to 8EiB since OsX 10.4 and the sparsebundle itself resides on that filesystem of that type also. So it's size limit should be 8EiB too. I see no reason, why a sparsebundle should have limits far less.

How can I create (resize) sparsebundles to, say, 20TB?

OS X Server

Posted on Jun 14, 2013 11:54 PM

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Answer 1

Pondini

Level 8

38,863 points

Jun 15, 2013 7:07 AM in response to ViennaAustria

I would be terrified to have a Time Machine sparsebundle anywhere near that large. Not in the neighborhood, not even in the suburbs. 😉

The larger they get (well, number of files more than total size), the more the odds of corruption increase, the longer verification takes, etc. I obviously don't know much about your setup, but I'd be looking for an alternative.

The only possibility I can suggest would be to change the size of the "band" files, but I have no idea if that would let you specify a larger maximum size. That's in the Info.plist file in the sparse bundle. I'd guess it should (or must) be a multiple of the number you find there, not something arbitrary. I've seen a couple of posts where people have done that, but have not tried it myself, so also don't know if there are other downsides.

Obviously, proceed with caution.

You might also want to look or post in the Mac OS X Technologies forum, where the UNIX gurus hang out.

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Answer 2

Jun 17, 2013 12:01 AM in response to Pondini

The problem begins with the sparesbundle itself. I cannot increase ITS (virtual) size beyond 16TiB. So I don't come to the point of enlarging the partition/filesystem that resindes in the sparsebundle or tryinf to mainipulate the size of the band files.

But maybe you hit the point somehow: maybe the blocksize of the virtual filesystems in sparsebundles is choosen very small. That would make sense to why Apple changed from simple files in a subfolder (around 10.6, I guess) to an entire filesystem in a virtualk disk. A smaller blocksize gives you less overhead.

I followed your advice and asked my question in the tech forum.

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Answer 3

Pondini

Level 8

38,863 points

Jun 17, 2013 5:06 AM in response to ViennaAustria

Have you tried creating the sparse bundle with a small maximum size (but empty), then changing the size of the band files, then changing the maximum size of the sparse bundle?

Again, I haven't tried that, but if the limit is really the number of band files instead of the total size, that would be the only way around it.

And, of course, it won't let you set the max larger than the size of the partition the sparse bundle is on.

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