Compare disk raid levels in terms of fault tolerance, write penalty and cost.

a) Why is there a write penalty on Raid5 and Raid6?

b) How is this write penalty typically overcome in modern disk arrays and SAN?

c) What does Raid 1+0 (Raid 10) mean?

d) Why is there little or no write penalty?

e) What is the ratio of usable storage to total storage in Raid 5?

f) What is the ratio of usable storage to total storage in Raid 10?