Created attachment 59968 [details] [review]
I'm not sure why the journal defauls to keeping 5% of the filesystem free. At a guess it follows the ext default of 5%.
Ofcourse whether the 5% is appropriate really depends on the system. On a big filesystem it's way too much (e.g. 50G on a 1T system seems a bit overkill), while on a somewhat conservatively sized filesystem it may be still too much.
As filesystems already have a reserved block count, which should be kept free for priviledged users it seems better to follow that. Which also means by default it followed the administrators or distributions preference for the filesystem setup.