File-system
Question 1 |
Consider a linear list based directory implementation in a file system. Each directory is a list of nodes, where each node contains the file name along with the file metadata, such as the list of pointers to the data blocks.Consider a given directory foo.
Which of the following operations will necessarily require a full scan of foo for successful completion?
Deletion of an existing file from foo | |
Opening of an existing file in foo | |
Creation of a new file in foo | |
Renaming of an existing file in foo |
Question 1 Explanation:
Renaming and creating a new file requires us to search the complete inode for duplicate names (to check if the same name already exists). There is no such problem in deleting and opening a file, as duplicate names are not possible while they are created.
Question 2 |
Consider a database implemented using B+ tree for file indexing and installed on a disk drive with block size of 4 KB. The size of search key is 12 bytes and the size of tree/disk pointer is 8 bytes. Assume that the database has one million records. Also assume that no node of the B+ tree and no records are present initially in main memory. Consider that each record fits into one disk block. The minimum number of disk accesses required to retrieve any record in the database is ______.
4 |
Question 2 Explanation:
Block factor = 4096/20 = 204
(1) Database BF = 1
No. of block = 106 } ➝ 1 block access from database
(2) ⎡106/204⎤ = 491
(3) ⎡491/204⎤ = 3
(4) ⎡3/204⎤ = 1
So, 1+3 = 4 disk accesses are required to retrieve any record in the database.
(1) Database BF = 1
No. of block = 106 } ➝ 1 block access from database
(2) ⎡106/204⎤ = 491
(3) ⎡491/204⎤ = 3
(4) ⎡3/204⎤ = 1
So, 1+3 = 4 disk accesses are required to retrieve any record in the database.
Question 3 |
A file system with a one-level directory structure is implemented on a disk with disk block size of 4K 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?
Theory Explanation. |
There are 3 questions to complete.