I saw the question bellow in a Computer Organization Practice Book for University exams.
Its given that, a magnetic disk has the following specifications:
Number of tracks = 1024
Number of sectors/track = 512
Bytes/Sector = 512
Disk Rotation Speed = 7200 RPM
Seek time = 9ms
The question given:
What is the data transfer rate?
The answer given:
My method of doing it:
Rotation speed: 7200RPM
So, 7200 rotations in 60 sec
1 rotation in 60/7200 sec.
Now, in 1 rotation only 1 track is read
1 track = 512 sectors = 512*512 bytes.
So, in 1 rotation 512*512 bytes is read.
i.e. In 1 Rotation 256 KB is read [ since, 512*512 bytes =256*1024 bytes ]
Thus, In 60/7200 sec 256 KB is read
In 1 sec 256*7200/60 KB is read
i.e 256*120 KB = 30 * 1024 KB = 30 MB
So, data transfer rate according to me: 30 MBPS.
But the explanation given in the book considered that in 1 rotation all tracks are read,
i.e In 1 rotation 1024*512*512 bytes is read and this is how they are getting the answer as 30 GBPS.
Kindly help me out here. Am I right? Or is the book correct?