Why Study File Structure Design? II. Memory versus Secondary Storage
Secondary storage such as disks can pack thousands of megabytes in a small physical location.
Computer Memory (RAM) is limited.
However, relative to Memory, access to secondary storage is extremely slow [E.g., getting information from slow RAM takes 120. 10-9 seconds (= 120 nanoseconds) while getting information from Disk takes 30. 10-3 seconds (= 30 milliseconds)]