# Disk Access Time | Computer Science homework help

Suppose a disk drive (a rather old one) has the following characteristics:

• 7 surfaces
• 1024 tracks per surface
• 512 sectors per track
• 2048 bytes per sector
• Track-to-track seek time of 8 milliseconds
• Rotation speed of 8500 RPM

a. What is the capacity of the drive?

b. Assume the drive has just been compacted. How long will it take to read a 4MB file? (Actually, the answer will depend somewhat on some uncontrollable factors, so you will need to make some assumptions and approximations to keep things simple. Just say what assumptions and approximations you are making. But be sure not to neglect any major contributors!)

A disk system is to be constructed using some number of identical disk drives, each of which can store up to T terabytes of data. A large database of size 4T terabytes is to be stored on the disk system. What is the minimum total number of disks that would be required for the system if the disk system is a:

a) RAID4 system?

b) RAID5 system?

c) RAID6 system?

d) RAID1 system?

e) RAID0 system?

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