File System

Question 1

Data is stored on

Answer 1

Physical devices, eg disks

Question 2

A file is a

Answer 2

Logical view of the data , perceived by the programmer

Question 3

A file system creates

Answer 3

An interface between users and files

Question 4

A file allocation method

Answer 4

Refers to how disk blocks are allocated & organized for files on the disk

Question 5

Contiguous allocation

Answer 5

Each file occupies set of contiguous blocks

Question 6

Pros of contiguous allocation

Answer 6

Best performance in most cases
Simple- only starting location (block #) and length (number of blocks) are required

Question 7

Cons of contiguous allocation

Answer 7

Finding space for file
estimating a file size at creation, or growing it
External fragmentation
Compaction

Question 8

Linked Allocation

Answer 8

Each file is a linked list of disk blocks: blocks may be scattered anywhere on the disk

Question 9

Pros of linked allocation

Answer 9

Simple, only need starting address
Free-space management system- no waste of space
Defragmentation not necessary for file allocation

Question 10

Cons of linked allocations

Answer 10

No random access, locating a block can take many disk seek & I/O
Extra space required for pointers
Clusters
Reliability: What if a pointers gets corrupted

Question 11

File Allocation Table

Answer 11

Beginning of volume has table indexed by block number

Question 12

Indexed Allocation

Answer 12

Brings all pointers together into the index block, to allow random access to file blocks

Question 13

Pros of indexed allocation

Answer 13

Supports direct access
Prevents external fragmentation

Question 14

Cons of indexed allocation

Answer 14

High pointer overhead -> wasted space

Question 15

What is wrong with too big of index block

Answer 15

Waste of space for small files

Question 16

What is wrong with too small of index block

Answer 16

Size of file will be limited

Question 17

What type of file access type to use contiguous?

Answer 17

Great for sequential and random

Question 18

What type of file access type to use Linked?

Answer 18

Good for sequential, not random

Question 19

What type of file access type to use Indexed

Answer 19

More complex

Question 20

Free-Space list

Answer 20

The system maintains it to record all free disk blocks

Question 21

Free-Space list implemented using

Answer 21

Linked List
Bit Vectors
Grouping
Counting

Question 22

What does a file system provide

Answer 22

Organized and efficient access to data on secondary storage

Question 23

File control block

Answer 23

metainformation about files

Question 24

Directories provide

Answer 24

A way for user to organize their files
A convenient file name space for both users and file systems

Question 25

A directory is typically

Answer 25

just a file that happens to contain special metadata

Question 26

Directory =

Answer 26

list of (name of file, file attributes)

Question 27

Directory attributes include

Answer 27

Size, protection, location on disk, creation time, access time

Question 28

The directory list is usually

Answer 28

unordered (effectively random)

Question 29

Navigation through trees relies on

Answer 29

pathnames

Question 30

absolute pathname start from

Answer 30

the root

Question 31

relative pathnames start from

Answer 31

current working directory

Question 32

.

Answer 32

current directory

Question 33

..

Answer 33

parent directories

Question 34

Pathname translation, how does it open directory?

Answer 34

Opens directory searches for next word and gets location of that

Question 35

In opening directories, what is checked at each step

Answer 35

Permissions

Question 36

Directory is a special file that containes

Answer 36

list of names of files and their inode numbers

Question 37

"A file is in a directory"

Answer 37

Directory has a link to the inode of the file

Question 38

"A directory contains a subdirectory"

Answer 38

Directory has a link to the inode of the subdirectory

Question 39

"A directory has a parent directory"

Answer 39

Entry of the directory has a link to the inode of the parent directory

Question 40

Inode

Answer 40

Structure maintaining all metadata about a file (or directory), except for name

Question 41

Inode number

Answer 41

unique ID of inode

Question 42

Hard Links

Answer 42

Creates another file with a link to the same underlying inode; an entry inside a directory with an inode

Question 43

Soft link (symbolic link)

Answer 43

A link to another name in the file system