Question

Really don't know what its about...

Course in operating system, file system

Question 2. File Systems (10 marks) (a) Consider a 32GB hard disk and a FAT file system with 24 bits cluster (block) address. What is the minimum block (cluster) size in order to fully utilize all space in the hard disk? (3 marks) (b) Consider an index-based file system with the inode containing 64 direct pointers, 1 indirect pointer, and 1 double-indirect pointer. Suppose the size of a disk block is 1024 bytes, an inode takes 1 disk block and each pointer takes 4 bytes. i) What is the maximum file size under this setting? Instead of showing the final number, shows the equation to reach your answer instead. (That is, you don't need to use a calculator to compute the final result but shows us something like 642 1024 is better) (3 marks) ii) Assume no caching, the Inode table is in memory, and the inode number of a file X is known already. How many disk accesses does it take to read the 3000321-th byte of file X? Justify your answer. (4 marks)

Answer 1

(a) A 32 GB disk has 2^35 bytes of storage;

If each entry in the FAT has 24 bits block address, then there can be at most 2^24 blocks, so each block must be

2^35/2^24 = 2^11 bytes = 2KB

(b)

(i) An indirect block has 1024 bytes * 1 index/4 bytes = 256 pointers
So a file has at most 64 + 256 + 256*2 blocks and (64 + 256 * 256^2) * 1024 bytes.

(ii) Block 3000321 is block number on Block Number = 3000321/1024 =  2930, which means we have to read the inode, the 2-level index, a direct index, and the data block. 4 reads.