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File System IO and Protection · Operating Systems · GATE CSE

Marks 1
16
Marks 2
21
Marks 5
7
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Marks 1

1
Suppose a disk has 201 cylinders, numbered from 0 to 200. At some time the disk arm is at cylinder 100, and there is a queue of disk access requests for cylinders 30, 85, 90, 100, 105, 110, 135 and 145. If Shortest-Seek Time First (SSTF) is being used for scheduling the disk access, the request for cylinder 90 is serviced after servicing ____________ number of requests.
GATE CSE 2014 Set 1
2
A FAT (file allocation table) based file system is being used and the total overhead of each entry in the FAT is $$4$$ bytes in size. Given a $$100\,\, \times \,\,{10^6}$$ bytes disk on which the file system is stored and data block size is $${10^3}$$ bytes, the maximum size of a file that can be stored on this disk in units of $${10^6}$$ bytes is __________.
GATE CSE 2014 Set 2
3
The data blocks of a very large file in the Unix file system are allocated using
GATE CSE 2008
4
Consider a disk pack with 16 surfaces, 128 tracks per surface and 256 sectors per track. 512 bytes of data are stored in a bit serial manner in a sector. The capacity of the disk pack and the number of bits required to specify a particular sector in the disk are respectively:
GATE CSE 2007
5
Normally user programs are prevented from handling $${\rm I}/O$$ directly by $${\rm I}/O$$ instructions in the for $$CPU$$ having explicit $${\rm I}/O$$ instructions, such $${\rm I}/O$$ protection is ensured by having the $${\rm I}/O$$ instructions privilege in $$CPU$$ with memory mapped $${\rm I}/O$$ there is no explicit $${\rm I}/O$$ instruction. Which one of the following is true for a $$CPU$$ with memory mapped $${\rm I}/O$$?
GATE CSE 2005
6
Consider an operating system capable of loading and executing a single sequential user process at a time. The disk head scheduling algorithm used is First Come First Served $$(FCFS).$$ If $$FCFS$$ is replaced by Shortest Seek Time First $$(SSTF),$$ claimed by the vendor to give $$50\% $$ better benchmark results, what is the expected improvement in the $${\rm I}/O$$ performance of user programs?
GATE CSE 2004
7
Using a larger block size in a fixed block size file system leads to
GATE CSE 2003
8
Which of the following requires a device driver?
GATE CSE 2001
9
Which of the following disk scheduling strategies is likely to give the best throughput?
GATE CSE 1999
10
Listed below are some operating system abstractions (in the left column) and the hardware components. Which matching pairs is correct?

$$\,\,\,\,\,\,\,\,\,\,$$$$\,\,\,\,\,\,\,\,\,\,$$$$\,\,\,\,\,\,\,\,\,\,$$List-$${\rm I}$$
(a) Thread $$\,\,\,\,\,\,\,\,\,\,$$$$\,\,\,\,\,\,\,\,\,\,$$(b) Virtual Address space
(c) File System $$\,\,\,\,\,\,\,\,\,\,$$(d) Signal

$$\,\,\,\,\,\,\,\,\,\,$$$$\,\,\,\,\,\,\,\,\,\,$$$$\,\,\,\,\,\,\,\,\,\,$$List-$${\rm II}$$
(1) Interrupt $$\,\,\,\,\,\,\,$$$$\,\,\,\,\,\,\,\,\,\,$$(2) Memory
(3) $$CPU$$ $$\,\,\,\,\,\,\,\,\,\,\,\,\,$$$$\,\,\,\,\,\,\,\,\,\,$$(4) Disk

GATE CSE 1999
11
Which of the following is true?
GATE CSE 1998
12
Which of the following devices should get higher priority in assigning interrupts?
GATE CSE 1998
13
When an interrupt occurs, an Operating System
GATE CSE 1997
14
The correct matching for the following pairs is

(a) Disk scheduling $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$(1) Round robin
(b) Batch processing $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ (2) $$SCAN$$
(c) Time sharing $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ (3) $$LIFO$$
(d) Interrupt processing $$\,\,\,\,\,\,\,\,\,\,\,$$(4) $$FIFO$$

GATE CSE 1997
15
The correct matching for the following pairs is
$$\,\,\,\,\,$$ List - $${\rm I}$$
(a) $$DMA$$ $$\,\,$$ $${\rm I}/O$$
(b) Cache
(c) Interrupt $${\rm I}/O$$
(d) Condition Code Register

$$\,\,\,\,\,$$ List - $${\rm II}$$
(1) High speed $$RAM$$
(2) Disk
(3) Printer
(4) $$ALU$$

GATE CSE 1997
16
$$I/O$$ redirection
GATE CSE 1997

Marks 2

1

Consider a disk with the following specifications: rotation speed of 6000 RPM, average seek time of 5 milliseconds, 500 sectors/track, 512-byte sectors. A file has content stored in 3000 sectors located randomly on the disk. Assuming average rotational latency, the total time (in seconds, rounded off to 2 decimal places) to read the entire file from the disk is _________

GATE CSE 2024 Set 2
2
Consider the following five disk access requests of the form (request id, cylinder number) that are present in the disk scheduler queue at a given time.

(P, 155), (Q, 85), (R, 110), (S, 30), (T, 115)

Assume the head is positioned at cylinder 100. The scheduler follows Shortest Seek Time First scheduling to service the requests.

Which one of the following statements is FALSE?
GATE CSE 2020
3
The index node (inode) of a Unix-like file system has 12 direct, one single-indirect and one double-indirect pointers. The disk block size is 4 kB , and the disk block address is 32 -bits long. The maximum possible file size is (rounded off to 1 decimal place) ___________ GB.
GATE CSE 2019
4
Consider a storage disk with $$4$$ platters (numbered as $$0, 1, 2$$ and $$3$$), $$200$$ cylinders (numbered as $$0, 1,$$ … , $$199$$), and $$256$$ sectors per track (numbered as $$0, 1, … , 255$$). The following $$6$$ disk requests of the form [sector number, cylinder number, platter number] are received by the disk controller at the same time: $$[120, 72, 2] , [180, 134, 1] , [60, 20, 0] , [212, 86, 3] , [56, 116, 2] , [118, 16, 1]$$

Currently the head is positioned at sector number $$100$$ of cylinder $$80,$$ and is moving towards higher cylinder numbers. The average power dissipation in moving the head over $$100$$ cylinders is $$20$$ milliwatts and for reversing the direction of the head movement once is $$15$$ milliwatts. Power dissipation associated with rotational latency and switching of head between different platters is negligible.

The total power consumption in milliwatts to satisfy all of the above disk requests using the Shortest Seek Time First disk scheduling algorithm is _______.

GATE CSE 2018
5
Consider a disk queue with requests for $${\rm I}/O$$ to blocks on cylinders $$47, 38, 121, 191,$$ $$87, 11, 92, 10.$$ The $$C$$-$$LOOK$$ scheduling algorithm is used. The head is initially at cylinder number $$63,$$ moving towards larger cylinder numbers on its servicing pass. The cylinders are numbered from $$0$$ to $$199.$$ The total head movement (in number of cylinders) incurred while servicing these requests is _________________ .
GATE CSE 2016 Set 1
6
Suppose the following disk request sequence (track numbers) for a disk with 100 tracks is given:

45, 20, 90, 10, 50, 60, 80, 25, 70.

Assume that the initial position of the R/W head is on track 50. The additional distance that will be traversed by the R/W head when the Shortest Seek Time First (SSTF) algorithm is used compared to the SCAN (Elevator) algorithm (assuming that SCAN algorithm moves towards 100 when it starts execution) is____________ tracks.
GATE CSE 2015 Set 1
7
Consider a main memory with five page frames and the following sequence of page references: 3, 8, 2, 3, 9, 1, 6, 3, 8, 9, 3, 6, 2, 1, 3. Which one of the following is true with respect to page replacement policies First In First Out (FIFO) and Least Recently Used (LRU)?
GATE CSE 2015 Set 1
8
A system contains three programs and each requires three tape units for its operation. The Minimum number of tape units which the system must have such that deadlocks never arise is _________.
GATE CSE 2014 Set 3
9
A file system with 300 G Byte disk uses a file descriptor with 8 direct block addresses, 1 indirect block address and 1 doubly indirect block address. The size of each disk block is 128 Bytes and the size of each disk block address is 8 Bytes. The maximum possible file size in this file system is
GATE CSE 2012
10
An application loads $$100$$ libraries at startup. Loading each library requires exactly one disk access. The seek time of the disk to random location is given as $$10$$ $$ms$$. Rotational speed of disk is $$6000$$ $$rpm.$$ If all $$100$$ libraries are loaded from random locations on the disk, how long does it take to load all libraries? (The time to transfer data from the disk block once the head has been positioned at the start of the block may be neglected).
GATE CSE 2011
11
Consider a disk system with $$100$$ cylinders. The requests to access the cylinders occur in following sequence:
$$4, 34, 10, 7, 19, 73, 2, 15, 6, 20$$
Assuming that the head is currently at cylinder $$50,$$ what is the time taken to satisfy all requests if it takes $$1$$ $$ms$$ to move from one cylinder to adjacent one and shortest seek time first policy is used?
GATE CSE 2009
12
For a magnetic disk with concentric circular tracks, the seek latency is not linearly proportional to the seek distance due to
GATE CSE 2008
13
Consider a disk drive with the following specifications:
$$16$$ surfaces, $$512$$ tracks/surface, $$512$$ sectors/track, $$1$$KB/Sector, rotation speed $$3000$$ rpm. The disk is operated in cycle stealing mode whereby whenever one $$4$$ byte word is ready it it's sent to memory; similarly, for writing, the disk interface reads a $$4$$ byte word from the memory in each $$DMA$$ cycle Memory cycle time is $$40$$nsec. The maximum percentage of time that the $$CPU$$ gets blocked during $$DMA$$ operation is:
GATE CSE 2005
14
In the index allocation scheme of blocks to a file, the maximum possible size of the file depends on
GATE CSE 2002
15
Formatting of floppy disk refers to
GATE CSE 1998
16
If the disk in (a) is rotating at $$3600$$ rpm, determine the effective data transfer rate which is defined as the number of bytes transferred per second between disk and memory.
GATE CSE 1995
17
The root directory of a disk should be placed:
GATE CSE 1993
18
A certain moving arm disk storage, with one head, has the following specifications.
Number of track/recording
Surface $$=200$$
Disk rotation speed $$=2400$$$$rpm$$
Track storage capacity $$=62,500$$ $$bits$$
The average latency of this device is
$$P$$ $$msec$$ and the data transfer rate is
$$Q$$ $$bits / sec.$$ Write the value of $$P$$&$$Q$$
GATE CSE 1993
19
State whether the following statement are TRUE or FALSE with reason. The data transfer between memory and $${\rm I}/O$$ devices using programmed $${\rm I}/O$$ is fasterthan interrrupt-driven $${\rm I}/O$$.
GATE CSE 1990
20
Disk requests come to disk driver for cylinders $$10,22,20,2,40,56$$ and $$38,$$ in that order at a time when the disk drive is reading from cylinder $$20.$$ The seek time is $$6msec$$ per cylinder. Compute the total seek time if the disk arm scheduling algorithm is
(a) First come first served
(b) Closest cylinder next.
GATE CSE 1989
21
On receiving an interrupt from an $${\rm I}/O$$ device the $$CPU$$:
GATE CSE 1987

Marks 5

1
Consider a disk with following specifications: $$20$$ surface, $$1000$$ tracks/surface, $$16$$ sectors/track, data density $$1$$ $$KB/sector,$$ rotation speed $$3000$$ $$rpm.$$ The operating system initiates the transfer between the disk and the memory sector-wise. Once the head has been placed on the right track, the disk reads a sector in a single scan. It reads bits from the sector while the head is passing over the sector. The read bits are formed into bytes in a serial $$=$$in-parallel-out buffer and each byte is then transferred to memory. The disk writing is exactly a complementary process. For parts $$(c)$$ and $$(d)$$ below, assume memory read-write time $$= 0.1$$ micro-second/ byte, interrupt driven transfer has an interrupt overhead $$= 0.4$$ microseconds, the $$DMA$$ initialization and termination overhead is negligible compared to the total sector transfer time. $$DMA$$ requests are always granted.

(a) What is the total capacity of the disk?
(b) What is the data transfer rate?
(c) What is the percentage of time the $$CPU$$ is required for this disk $${\rm I}/O$$ for byte-wise interrupts driven transfer?
(d) What is the maximum percentage of time the $$CPU$$ is held up for this disk $${\rm I}/O$$ for cycle-stealing $$DMA$$ transfer ?

GATE CSE 2001
2
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?

GATE CSE 2001
3
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?

GATE CSE 1996
4
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.
GATE CSE 1995
5
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: $$20$$
GATE CSE 1995
6
A certain moving arm disk-storage device has the following specifications:
Number of tracks per surface $$=4004$$
Track storage capacity $$=130030$$ bytes
Disk speed $$=3600$$ rpm
Average seek time $$=30$$ m secs.
Estimate the average latency the disk storage capacity and the data transfer rate.
GATE CSE 1990
7
Assuming the current disk cylinder to be $$50$$ and the sequence for the cylinders to be
$$1, 36, 49, 65, 53, 1, 2, 3, 20, 55, 16, 65$$ and $$78$$ find the sequences of servicing using
(i) shortest-seek time first $$(SSTF)$$
(ii) elevator disk scheduling polices.
GATE CSE 1990
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