Recent questions tagged disks - GATE Overflow

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 41 (Page No. 433)
A bitmap terminal contains $1600$ by $1200$ pixels. To scroll a window, the CPU (or controller) must move all the lines of text upward by copying their bits from one part of the video RAM to another. If a particular ... ? Putting a character on the screen takes $5\: \mu sec.$ How many lines per second can be displayed?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 7 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 40 (Page No. 433)
Many versions of UNIX use an unsigned $32$-bit integer to keep track of the time as the number of seconds since the origin of time. When will these systems wrap around (year and month)? Do you expect this to actually happen?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 11 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 39 (Page No. 433)
A system simulates multiple clocks by chaining all pending clock requests together as shown in Fig. 5-30. Suppose the current time is $5000$ and there are pending clock requests for time $5008, 5012, 5015, 5029,4$ ... $5017$ for $5033.$ Show the values of Clock header, Current time and Next signal at time $5023.$

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 7 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 38 (Page No. 432)
A computer uses a programmable clock in square-wave mode. If a $500\:MHz$ crystal is used, what should be the value of the holding register to achieve a clock resolution of a millisecond (a clock tick once every millisecond)? $100$ microseconds?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 10 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 36 (Page No. 432)
In the discussion on stable storage, a key assumption is that a CPU crash that corrupts a sector leads to an incorrect ECC. What problems might arise in the five crash-recovery scenarios shown in Figure 5-27 if this assumption does not hold?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 5 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 35 (Page No. 432)
In the discussion on stable storage, it was shown that the disk can be recovered to a consistent state (a write either completes or does not take place at all) if a CPU crash occurs during a write. Does this property hold if the CPU crashes again during a recovery procedure. Explain your answer.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 4 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 34 (Page No. 432)
In the discussion of stable storage using nonvolatile RAM, the following point was glossed over. What happens if the stable write completes but a crash occurs before the operating system can write an invalid block ... in the nonvolatile RAM? Does this race condition ruin the abstraction of stable storage? Explain your answer.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 5 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 33 (Page No. 432)
A personal computer salesman visiting a university in South-West Amsterdam remarked during his sales pitch that his company had devoted substantial effort to making their version of UNIX very fast. As an example, he ... measured was identical to what would be expected from first-come, first-served. Was the salesman lying?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 3 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 31 (Page No. 432)
Disk requests come in to the disk driver for cylinders $10, 22, 20, 2, 40, 6,$ and $38,$ in that order. A seek takes $6\: msec$ per cylinder. How much seek time is needed for First-come, first served. Closest cylinder next. Elevator algorithm (initially moving upward). In all cases, the arm is initially at cylinder 20.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 27 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 30 (Page No. 432)
A computer manufacturer decides to redesign the partition table of a Pentium hard disk to provide more than four partitions. What are some consequences of this change?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 6 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 29 (Page No. 432)
A disk manufacturer has two $5.25$-inch disks that each have $10,000$ cylinders. The newer one has double the linear recording density of the older one. Which disk properties are better on the newer drive and which are the same? Are any worse on the newer one?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 7 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 28 (Page No. 431)
Consider a magnetic disk consisting of $16$ heads and $400$ cylinders. This disk has four $100$-cylinder zones with the cylinders in different zones containing $160, 200, 240.$ and $280$ sectors, respectively. ... disk rotates at $7200$ RPM. Calculate the disk capacity, optimal track skew, and maximum data transfer rate.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 11 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 27 (Page No. 431)
If a disk has double interleaving, does it also need cylinder skew in order to avoid missing data when making a track-to-track seek? Discuss your answer.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 13 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 25 (Page No. 431)
What are the advantages and disadvantages of optical disks versus magnetic disks?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 5 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 24 (Page No. 431)
Why are optical storage devices inherently capable of higher data density than magnetic storage devices? Note: This problem requires some knowledge of high-school physics and how magnetic fields are generated.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 3 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 22 (Page No. 431)
Compare RAID level $0$ through $5$ with respect to read performance, write performance, space overhead, and reliability.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 8 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 21 (Page No. 431)
A RAID can fail if two or more of its drives crash within a short time interval. Suppose that the probability of one drive crashing in a given hour is $p.$ What is the probability of a $k$-drive RAID failing in a given hour?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 5 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 20 (Page No. 431)
RAID level $3$ is able to correct single-bit errors using only one parity drive. What is the point of RAID level $2$? After all, it also can only correct one error and takes more drives to do so.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 5 views

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19

Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 19 (Page No. 431)
Calculate the maximum data rate in bytes/sec for the disk described in the previous problem.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 9 views

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20

Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 18 (Page No. 431)
A disk rotates at $7200$ RPM. It has $500$ sectors of $512$ bytes around the outer cylinder. How long does it take to read a sector?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 9 views

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21

Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 17 (Page No. 431)
How much cylinder skew is needed for a $7200$-RPM disk with a track-to-track seek time of $1\: msec$? The disk has $200$ sectors of $512$ bytes each on each track.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 17 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 16 (Page No. 431)
Why are output files for the printer normally spooled on disk before being printed?

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 6 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 5 Question 14 (Page No. 430)
In which of the four I/O software layers is each of the following done. Computing the track, sector, and head for a disk read. Writing commands to the device registers. Checking to see if the user is permitted to use the device. Converting binary integers to ASCII for printing.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 7 views

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24

Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 48 (Page No. 336)
Implement a simulated file system that will be fully contained in a single regular file stored on the disk. This disk file will contain directories, i-nodes, free-block information, file data blocks, etc. Choose ... directories, create/delete/open files, read/write from/to a selected file, and to list directory contents.

asked Oct 28 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 5 views

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25

Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 45 (Page No. 336)
Write a program that scans all directories in a $UNIX$ file system and finds and locates all i-nodes with a hard link count of two or more. For each such file, it lists together all file names that point to the file.

asked Oct 27 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 5 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 44 (Page No. 336)
Write a program that starts at a given directory and descends the file tree from that point recording the sizes of all the files it finds. When it is all done, it should print a histogram of the file sizes using a bin width specified as a ... sizes of $0$ to $1023$ go in one bin, $1024$ to $2047$ go in the next bin, etc.).

asked Oct 27 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 4 views

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27

Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 43 (Page No. 336)
Write a program that reverses the bytes of a file, so that the last byte is now first and the first byte is now last. It must work with an arbitrarily long file, but try to make it reasonably efficient.

asked Oct 27 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 6 views

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28

Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 42 (Page No. 336)
In many UNIX systems, the i-nodes are kept at the start of the disk. An alternative design is to allocate an i-node when a file is created and put the i-node at the start of the first block of the file. Discuss the pros and cons of this alternative.

asked Oct 27 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 4 views

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29

Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 41 (Page No. 336)
How many disk operations are needed to fetch the i-node for a file with the path name /usr/ast/courses/os/handout.t? Assume that the i-node for the root directory is in memory, but nothing else along the path is in memory. Also assume that all directories fit in one disk block.

asked Oct 27 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 6 views

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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 40 (Page No. 336)
A UNIX file system has $4-KB$ blocks and $4-$byte disk addresses. What is the maximum file size if i-nodes contain $10$ direct entries, and one single, double, and triple indirect entry each?

asked Oct 27 in Operating System by Lakshman Patel RJIT Veteran (54.8k points) | 6 views

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