1. Classify each of the following statements as true or false: a. Allocation of contiguous disk space for a sequential-access file leads to more efficient file processing than allocation of noncontiguous disk space.
b. Cycles in the directory structure create diffi- culties with the file deletion operation.
c. Absolute path names for two different files cannot be identical, whereas their relative path names could be identical.
d. The purpose of the file control block (FCB) is to facilitate a file open operation; the FCB can be deleted immediately after the file is opened.
e. When a file is closed after updating, the directory containing the file may have to be updated as well.
f. Maintaining a file’s file map table (FMT) in memory while the file is being processed reduces the number of disk accesses during file processing.
g. During creation of a new file in a mounted file system, the file is allocated disk space in the logical disk used by the mounted file system.
h. The effect of mounting a file system is similar to that of setting up a link in the directory structure, except that the effect is obliterated when the file system is unmounted.
i. When a user updates the data in a singleimage mutable file, changes made to the file are not immediately visible to users concurrently using the file.
j. When a fault occurs, a single incremental backup is adequate for restoring the entire file system to a previous consistent state.
k. Journaling incurs overhead during operation of a file system.
l. A virtual file system permits use of many file systems in a computer; however, these file systems cannot be used concurrently.
2. Classify each of the following statements as true or false: a. When parity bits are used for reliable recording/reading of data, an error correction code requires more parity bits than an error detection code.
b. Restricting the disk space allocation for a file to a cylinder group—which is a group of consecutive cylinders on a disk—reduces disk head movement while the file is processed.
c. RAID level 4, which uses block-interleaved parity, provides parallelism between small I/O operations.
d. Blocking of records speeds up processing of sequential files.
e. Buffering of records speeds up processing of direct-access files.
f. The SCAN disk scheduling policy suffers from starvation.
g. The physical IOCS provides a method to avoid the busy wait condition while a process awaits completion of its I/O operation.
h. If tx < tp, it is possible to reduce tw to tc through appropriate buffering and blocking.
i. Using a blocking factor of m reduces the effective I/O time per logical record by a factor of m.
SUBJECT : OPERATING STSTEM INTERNALS