The BAT area follows the free list. The size and number of BATs is
defined when the filesystem is formatted. BATs are
arrays of block addresses for the blocks that contain the data of the
file. The number of BATs gives a hard upper limit to the number of
files permitted. Usually this is set to equal the number of directory
entries. There is little point in making it larger, but it may be
useful to set it smaller if the minimal size of the directory exceeds
the desired maximum number of files.
The size of each BAT represents a hard upper limit on the size
of a file. BAT size should be set to cover the expected range of file
sizes. Larger data sets can be handled at application level by
splitting the data across several files.