Problem
Given total 8 4TB SSDs with the following two possible configurations: (a) RAID 10 and (b) 7+1 RAID 5. Assume the per-SSD failure probability is 1x10-9, calculate the data loss probability under these two possible configurations. Assume all the SSDs have the same price, calculate the ratio of effective storage cost of these two possible configurations (note: effective storage cost is defined as the "amount of user data per dollar"). Do you have any good reason to choose the 1st configuration (i.e., RAID 10)?