def customize(self, size, requested_filesystem):
"""
increase the sum of all file sizes by an empiric factor
"""
if requested_filesystem.startswith('ext'):
size *= 1.5
file_count = self.accumulate_files()
inode_mbytes = \
file_count * Defaults.get_default_inode_size() / 1048576
size += 2 * inode_mbytes
elif requested_filesystem == 'btrfs':
size *= 1.5
elif requested_filesystem == 'xfs':
size *= 1.2
return int(size)
