The rest of the space allocated to the file system is occupied by data blocks, also called storage blocks. The size of these data blocks is determined at the time a file system is created. Data blocks are allocated, by default, in two sizes: an 8-Kbyte logical block size, and a 1-Kbyte fragmentation size.
For a regular file, the data blocks contain the contents of the file. For a directory, the data blocks contain entries that give the inode number and the file name of the files in the directory.