# Question: Hard Drives It is generally recognized that it is wise

Hard Drives It is generally recognized that it is wise to back up computer data. Assume that there is a 2% rate of disk drive failure in a year (based on data from various sources, including “Failure Trends in Large Disk Drive Population,” by Pinhero et al. of Google, Inc.).

a. If you store all of your computer data on a single hard disk drive, what is the probability that the drive will fail during a year?

b. If all of your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that both drives will fail during a year?

c. If copies of all of your computer data are stored on three independent hard disk drives, what is the probability that all three will fail during a year?

d. Describe the improved reliability that is gained with backup drives.

a. If you store all of your computer data on a single hard disk drive, what is the probability that the drive will fail during a year?

b. If all of your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that both drives will fail during a year?

c. If copies of all of your computer data are stored on three independent hard disk drives, what is the probability that all three will fail during a year?

d. Describe the improved reliability that is gained with backup drives.

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