Created attachment 522553 [details]
Disk Usage (include F15 partition)
I have a test system which boots 7 operating systems. The system is used for testing (ie, compile and self tests). (I don't have hardware with enough ass to run VMs).
F15 has a 16 GB slice in an extended partition. However, the one (and only) time I was able to log in after installation claimed the disk was full. F15 also erroneously reported its size as 8 GB and that all 8 GB were in use.
Attached is a Disk Utility screen capture of the test machine, and a capture of Disk Usage Analyzer of the F15 partition. Both captures were taken from Ubuntu 11. Notice Ubuntu reports 16 GB slice, and only 4 GB in use.
Checking the F15 partition using a foreign operating system was OK. Unfortunately, I cannot log into F15 any longer to test natively.
Created attachment 522554 [details]
Disk Usage Analyzer (F15 partition)
Honestly, it looks like your filesystem size doesn't match your partition size.
What does 'df' say if you mount it?