Question

Q1) A particular implementation of UNIX operating system provides the file structure modelled in the Figure 1. Here the i-node for the file contains certain information such as the access permissions for the file. This is followed by the entries that contain information about where the file is located on the storage device. The first 10 entries are the addresses of blocks where actual data for the file are stored. If block can contain 512 bytes of information, then these 10 direct blocks can hold up to 512 x 10-5120 bytes of data When the size of the file exceeds 10 blocks, the eleventh entry provides access to, or points to, an indirect block. This indirect block contains the addresses for 128 additional blocks where data can be stored. If this indirect block is used, the size of the file can be as large as 10+128 138 blocks, and it can contain up to 512 x 13870, 656 bytes of Various Blocks 128 Indirect block information 10 Blocks a) A twelfth entry is needed if more than 138 blocks are required for the file. This entry contains the address df double indirect block that in turn contains the addresses of 128 indirect blocks. As noted earlier, each of these indirect blocks contains the address for 128 blocks where data can be stored. If a file uses 12 entries in its i-node, what is its 12 13 128 128 128 128 block blocks maximum size (in bytes)? 128 b) When the file must be even larger than that provided by 12 entries, a thirteenth entry is needed. It provides the address to a triple indirect block that points to 128 double indirect blocks (as shown in Figure 1). Determine the maximum file size, for implementation of this UNIX operating 128 128 Triple 128 128 system under these conditions, (in bytes) 128 Figure 1 Answer Q1)

Answer 1

A.

If the 12th block is used, size of the file can be = 10 + 128+ 128*128

=16,522

Max size it can store = 512*16522

= 8,459,264 bytes

B.

If the 13th block is used, size of the file can be = 10 + 128 + 128*128 + 128*128*128

= 2,113,674

Max size it can store = 512*2113674

=1,082,201,088 bytes