Ciência da Computação

gugarthur
(usa Fedora)

Enviado em 21/11/2009 - 00:01h

Não sei se essa é a comunidade adequada para fazer essas perguntas, mas aí vai. Sou aluno de Ciência da Computação e gostaria de saber se alguém poderia me ajudar a responder essas perguntas:

11.4 Consider a disk with N tracks numbered from 0 to (N - 1) and assume that requested
sectors are distributed randomly and evenly over the disk.We want to calculate the
average number of tracks traversed by a seek.
a. First, calculate the probability of a seek of length j when the head is currently positioned
over track t. (Hint: This is a matter of determining the total number of combinations, recognizing that all track positions for the destination of the seek
are equally likely.)
b. Next, calculate the probability of a seek of length K. (Hint: This involves the summing
over all possible combinations of movements of K tracks.)
c. Calculate the average number of tracks traversed by a seek, using the formula for
expected value
Hint: Use the equalities
d. Show that for large values of N, the average number of tracks traversed by a seek
approaches N/3.

11.7 Calculate how much disk space (in sectors, tracks, and surfaces) will be required to
store 300,000 120-byte logical records if the disk is fixed-sector with 512 bytes/sector,
with 96 sectors/track, 110 tracks per surface, and 8 usable surfaces. Ignore any file
header record(s) and track indexes, and assume that records cannot span two
sectors.