Full disk backup size is 2x what Finder says I have *in total*...why?
So, I admit it, I'm a Unix guy - it's one of the reasons OS X appealed to me in the first place. When I went to test my new external 320gb FireWire drive, I thought I'd make a full backup of my MacBookPro (10.4.11) using the tool I know best....tar. I mounted the drive and then did the backup from the command line:
cd /
sudo tar cvjf /Volumes/BigPartition/Save_All.tbz .
Hey, not pretty, but it worked. Except the backup tar file was 15GB - which was really odd since it's being compressed with Bzip and Finder says I'm using only 14GB _in total_ on my disk, and I'd expect a compressed backup to be much smaller - maybe 7GB. So it was 2x bigger than I thought it would be.
So I did it again, but this time without compression in case that was the problem (compressing already compressed data, etc). And it took up 31GB. So I'm REALLY confused here:
1) Am I using a whole lot more (17GB more!) disk than the Finder claims I am? OR
2) Is my 'tar' command saving files that don't really exist (like copies of virtual memory, etc.) that make it save 2x-3x as the actual data size would save as? OR
3) Is there some other explanation I'm not getting on this?
If #2, what's a tar command I could use to save the "real" system and data, but nothing else? Meaning, which directories/files do I need to exclude to save just the system and data I need to do a full restore, but no more?
Finally, besides the Backup app included with the OS, is there another tool/script I should be using to do a full system backup to my external drive?
thanks....and please scale the technical level of your answer to someone who programs in assembly language for fun. :}
cd /
sudo tar cvjf /Volumes/BigPartition/Save_All.tbz .
Hey, not pretty, but it worked. Except the backup tar file was 15GB - which was really odd since it's being compressed with Bzip and Finder says I'm using only 14GB _in total_ on my disk, and I'd expect a compressed backup to be much smaller - maybe 7GB. So it was 2x bigger than I thought it would be.
So I did it again, but this time without compression in case that was the problem (compressing already compressed data, etc). And it took up 31GB. So I'm REALLY confused here:
1) Am I using a whole lot more (17GB more!) disk than the Finder claims I am? OR
2) Is my 'tar' command saving files that don't really exist (like copies of virtual memory, etc.) that make it save 2x-3x as the actual data size would save as? OR
3) Is there some other explanation I'm not getting on this?
If #2, what's a tar command I could use to save the "real" system and data, but nothing else? Meaning, which directories/files do I need to exclude to save just the system and data I need to do a full restore, but no more?
Finally, besides the Backup app included with the OS, is there another tool/script I should be using to do a full system backup to my external drive?
thanks....and please scale the technical level of your answer to someone who programs in assembly language for fun. :}
MacBook Pro, Mac OS X (10.4.11)
