When doing a disk read or write, it takes a while for the disk head to
move to the part of the disk where the data are located. This time is called
SEEK TIME the seek time and it averages 5 ms for typical disks. No data are being
transferred during the seek. To maximize data transfer rates, chunks of
data that will be read together should therefore be stored contiguously on
disk. For example, using the numbers in Table 4.1 it may take as little as
0.2 seconds to transfer 10 megabytes (MB) from disk to memory if it is
stored as one chunk, but up to 0.2 + 100 × (5 × 10−3) = 0.7 seconds if it
is stored in 100 noncontiguous chunks because we need to move the disk
head up to 100 times.