difference 'f_files' - 'f_ffree', which is the current number of
used objects. This is what "df" displays.
-The number of OST free objects is divided by the filesystem-wide
+The number of OST free objects is divided by the file-system-wide
default stripe count (i.e. the expected number of OST objects used per
MDT file), so that 'f_ffree' represents the expected minimum number of
files that can be created at the current time.