You have a harddrive with 8GB of data stored on it, and the files are fragmented. The average size of a file is 16KB. To defragment the files, the OS copies a file to a clean area of the drive reserved for compacting the drive, then writes the file back to contiguous sectors in the main storage area so there are no fragments in the file. Average seek time and rotational delay for the drive are 5 and 4 milliseconds respectively, with a transfer rate of 4MB/sec.

How long does it take to write one file to the compression area and back to the main storage area of the disk?

There are total hard disk size is 8 GB = 8 * 1024 * 1024 * 1024 Bytes

Average file size is 16 KB = 16 * 1024 Bytes

We have given average seek time is 5ms and avg. rotational delay time is 4ms

We have Transfer Rate is given as 4MB / sec = 4 / ms

We know Total time taken to read or write from and to disk can be calculated as

Total time = filesize * (seek time + avg. rotational latency + data transfer time)

We have given data for file is 16 KB i. e. 16 * 1024 (1KB = 1024 Bytes)

So we can calculate as

Total Time = Total Time to compress the file + Total Time to write back

Total Time = 16*1024 * (5 + 4+4)

=16*1024*13 ms