While the most simplistic design is highly inefficient, advanced or hybrid implementations of free-space bitmaps are used by some modern file systems[which?].
If the file were subsequently truncated down to 8 KiB, the final sector's bit would be set back to zero, indicating that it is again available for use.
To address this, real-world implementations of free-space bitmaps will find ways to centralize information on free space.
If the combined size of the summary array and bitmap is greater than can readily be stored in memory, and a large number of files with scattered sectors are freed, an enormous amount of disk access is necessary to find all the sectors, decrement the summary counter and flip the bits back to zero.
This greatly reduces the benefits of the bitmap, as it is no longer performing its function of summarizing the free space rapidly without reading from the disk.