Seemingly simple question - are Sparsebundle Backups Smaller/Compressed vs. Source?
 

This seems like one of those questions that's so obvious it would be instantly findable, but the user guide, this forum's search, and the wide world of google have all left me unsure.

My situation is as follows:

* Backup up main desktop HD to a sparsebundle DMG on a largish firewire external. (then backing *that* up to the cloud via Mozy, FWIW)

* Settings: SuperDuper >> Copy "Macintosh HD" to "NAME_OF_SPARSEBUNDLE" >> "Backup - all files

* No other settings except smart update is selected under "Advanced" -- it's basically right out of the box otherwise.

* The Mac's internal HD shows 80GB used

* The sparse bundle shows 64.6GB as its size.

*** This seems like too much of a spread (15GB!) to account for the normal smallish stuff like caches and a few certain system files, etc. I have done a run through the source HD looking for an errant gigantic cache file or similar and don't see anything suspicious.


I wasn't aware of heavy compression for Sparse Bundles, not that heavy at least. Also not aware of any hidden setting for excluding files/folders from my backup outside of a script, which this isn't, unless it's some kind of default script.

So -- guesses on what accounts for the size discrepancy, anything I should I be nervous about or fix?



[SYSTEM: Mac, 2ghz Intel Core 2 Duo / 4GB SDRAM / OSX 10.5.8 / SUPERDUPER 2.6.2]

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No, bundles are not compressed. But "What's going to happen?" pretty clearly indicates that we skip files like VM Swap Files, Temporary files and the like...

Thanks for the reply. It's the "and the like..." that is perhaps what I'm wondering about. I suppose running Mozy I've seen some pretty severely large VM Swap files for sure, but 15GB discrepancy still is quite a lot. I'm seeing well under 5 in swaps right now.

I'll do a controlled experiment and try again and compare and see what happens. But besides swaps it's just stuff like what, browser caches, trashes, etc? Some caches are more important than others of course.... :D ...especially stuff like Adobe Bridge caches for those of us dealing with a thousand camera raw files at a time, that kind of thing.
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You can see exactly what we skip by examining the copy scripts...