Consider a file system that us

If all extents are of the same size, and the size is predetermined, then it simplifies the block allocation scheme. A simple bit map or free list for extents would suffice. If the extents can be of any size and are allocated dynamically, then more complex allocation schemes are required. It might be difficult to find an extent of the appropriate size and there might be external fragmentation. One could use the Buddy system allocator discussed in the previous chapters to design an appropriate allocator. When the extents can be of a few fixed sizes, and these sizes are redetermined, one would have to maintain a separate bitmap or free list for each possible size. This scheme is of intermediate complexity and of intermediate flexibility in comparison to the earlier schemes.