Consider a disk with the $$100$$ tracks numbered from $$0$$ to $$99$$ rotating at $$3000$$ $$rpm.$$ The number of sectors per track is $$100.$$ the time to move the head between two successive tracks is $$0.2$$ milliseconds.

(a) Consider a set of disk requests to read data from tracks $$32, 7, 45, 5$$ and $$10.$$ Assuming that the elevator algorithm is used to schedule disk requests, and the head is initially at track $$25$$ moving up (towards larger track numbers), what is the total seek time for servicing the requests?
(b) Consider an initial set of $$100$$ arbitrary disk requests and assume that no new disk requests arrive while servicing these requests. If the head is initially at track $$0$$ and the elevator algorithm is used to schedule disk requests, what is the worst case time to complete all the requests?

A file system with a one-level directory structure is implemented on a disk with disk block size of $$4$$ K bytes. The disk is used as follows:

Disk-block $$0:$$ File Allocation Table, consisting of one $$8$$-bit entry per date block, representing the data block address of the next date block in the file:

Disk block $$1:$$ $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ Directory, with one $$32$$ bit entry per file:
Disk block $$2:$$ $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ Data block $$1;$$
Disk block $$3:$$ $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ Data block $$2;$$ etc.

(a) What is the maximum possible number of files?
(b) What is the maximum possible file size in blocks?

The head of a moving head disk with $$100$$ tracks numbered $$0$$ to $$99$$ is currently serving a request at tract $$55.$$ If the queue of requests kept in $$FIFO$$ order is $$10, 70, 75, 23, 65$$ Which of the two disk scheduling algorithms $$FCFS$$ (First Come First Served) and $$SSTF$$ (Shortest Seek Time First) will require less head movement? Find the head movement for each of the algorithms.

If the overhead for formatting a disk is $$96$$ bytes for $$40000$$ bytes sector, Compute the unformatted capacity of the disk of the following parameters:
Number of surface: $$8$$
Outer diameter of the disk : $$12cm$$
Inner diameter of the disk: $$4cm$$
Inter track space: $$0.1mm$$
Number of sectors per track: $$20$$