Editing Ext2 (section)

===Allocating data===
When a new file or directory is created, ext2 must decide where to store the data. If the disk is mostly empty, then data can be stored almost anywhere. However, clustering the data with related data will minimize seek times and maximize performance.

ext2 attempts to allocate each new directory in the group containing its parent directory, on the theory that accesses to parent and children directories are likely to be closely related. ext2 also attempts to place files in the same group as their directory entries, because directory accesses often lead to file accesses. However, if the group is full, then the new file or new directory is placed in some other non-full group.

The data blocks needed to store directories and files can be found by looking in the data allocation bitmap. Any needed space in the inode table can be found by looking in the inode allocation bitmap.