[lug] df discrepancies between used, available and total size

[karl horlen]

>>  Assuming this is ext2 (or ext3 or ext4), then yes, it's reserved.
>>  Dunno about XFS and other alternate FSs.  BTRFS, in particular, has a
>>  very wonky concept of "free space".
> 
> A while back, when formatting a couple of 1.5 TB USB drives, I noticed 
> that EXT4 reserved noticeably more space than XFS. I don't recall the 
> exact number, but it was on the order of several GB.

yeah.  this was my first ext4 install.  my older stuff has mostly if not all been ext3.  i'd heard some criticisms of ext4 so kept with the old ext3 for some years.  just decided to move ahead with it as the default at install.  perhaps it reserves more space by default?