Linked-list allocation gives the ultimate in flexibility and disk utilization, but after a while, performance slows down. When files are deleted, sectors are reclaimed and stored on a free sector list, which serves as a pool from which the operating system can get a chunk of disk memory when it needs it. Over time, these sectors will be sprinkled over the entire disk, and files that are formed from them will likewise pepper the disk, causing the reading of a file to involve many seeks and slowing it down. Minimizing this effect is one of the tasks of operating systems designers.