A file control block contains the information about a

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A file control block contains the information about a) file ownership b) file permissions c) location of file contents d) all of the mentioned Answer: d 10) Management of metadata information is done by a) file-organisation module b) logical file system c) basic file system d) application programs Answer: b 2
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2. (24 points) Please answer the following questions in a few sentences. 1) (5 points) Discuss the factors affecting page size selection. Answer: Fragmentation, Page table size, Resolution, I/O overhead, Number of page faults, Locality, TLB size and effectiveness 2) (6 points) Discuss the pros and cons of the three block allocation methods(contiguous allocation, link and index) for both sequential and random file access. Answer: Contiguous Sequential - Works very well as the file is stored contiguously. sequential access - Simply involves traversing the contiguous disk blocks. Contiguous Random -Works very well as you can easily determine the adjacent disk block containing the position you wish to seek to. Linked Sequential - Satisfactory as you are simply following the links from one block to the next. Linked Random - Poor as it may require following the links to several disk blocks until you arrive at the intended seek point of the file. Indexed Sequential - Works well as sequential access simply involves sequentially accessing each index. Indexed Random - Works well as it is easy to determine the index associated with the disk block containing the position you wish to seek to 3) (4 points) How does FAT allocation improve over the linked allocation. Answer: FAT has one entry for each disk block and is indexed by block number. While accessing a block that is stored at the middle of a file, its location can be determined by chasing the pointers stored in the FAT as opposed to accessing all of the individual blocks of the file in a sequential manner to find the pointer to the target block. FAT can be cached. Random (direct) access time is improved, because the disk head can find the location of any block by reading the information in the FAT, instead of moving through blocks stored on the disk in the linked-allocation scheme. 4) (6 points) Briefly describe, 3 each, on-disk and in-memory data structures that OS commonly use. Answer: on-disk : Any three below e.g. FAT, FFS, ext2, ext3, etc - Boot control block (per volume) contains info needed by system to boot OS from that volume If the disk does not contain an OS, this block can be empty Usually the first block of a volume. In UFS, it is called the boot block. In NTFS, it is the partition boot sector
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