Size of Time Machine backup not as big as source?

[0071284]

Hello,

I just ran a time machine backup (to a time capsule), the first one on this drive. I am concerned it is not working properly. I have selected to exclude only my iTunes folder, leaving a backup size of 135 GB. The backup is complete, and the Sparse Disk Image Bundle size is 90 GB.

Why is there a 45 GB difference between the size of what is supposed to be backed up and the backup?


Thanks for any help.


-MS

 

[johnhurley]

Why is there a 45 GB difference between the size of what is supposed to be backed up and the backup?

Compression probably? Backups can be compressed to save space ... not sure if Time Machine has a setting to enable/disable that feature.

 

[0071284]

Meaning I am losing data in my image files?
That's no good.

 

[Partron22]

Meaning I am losing data in my image files?

No, if it were lossy compression, the elves would be hearing our cries of pain in Rivendell by now.

Some of that 45GB could come from differences in block size between the two volumes. Some may come from the stripping of unneeded 'versions' of a file before it gets sent to the backup. Your older backups already contain some file versions, so there's no need to duplicate that data.

 

[0071284]

Time Machine does not do any compression.

https://discussions.apple.com/thread/3540552?start=0&tstart=0

 

[0071284]

Looks like the reason is a 35 GB cache for Adobe Camera Raw.