A disk has the following specification: - Number of bytes per sector = 512 - Num

Question

A disk has the following specification:

- Number of bytes per sector = 512

- Number of sectors per track = 256

- Number of platters = 12, each platter with 2 surfaces

- Number of cylinders = 8,192

- Spindle speed = 10,000 rpm

- Average seek time = 10 milliseconds

A file has 50,000 fixed-length data records. Each record has 256 bytes. What is the total time in minutes (including the average seek time, rotational delay and transfer time) to read the file sector by sector in random (assuming the file is stored in random sectors)?

a. 4.5 minutes b. 3.4 minutes c. 2.7 minutes d. 1.8 minutes e. 5.4 minutes

Explanation / Answer

given

sector size=512
sectors per track=256
averarge seek time=10ms

rotational spped =10000 rpm
       =60/10000 seconds per rotation
       =6 milliseconds per rotation

seektime=avg seek time=10ms

rotaional delay =since we are accessing a single disk at a time
       =time for one rotation/2
       =6/2
       =3 ms per rotation.

track capacity(transferrate)=512* 256*12*2=3.14 mbs
tranferTime=(1/256)*60=0.23

total time= avg seektime+rotational delay+transferTime=10+3+0.23=13.23

so near to the above is e.5.4

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