Question

1 Mark Question Two Consider a file system on a disk that has both logical and physical block sizes of 512 tebytes. Assume that the information about each file is already in memory. For each of the three allocation strategies (contiguous, linked, and indexed), answer these at questions: a. How is the logical-to-physical address mapping accomplished in this system? (For the indexed allocation, assume that a file is always less than 512 blocks long.) b. If we are currently at logical block 10 (the last block accessed was block 10) and want to access logical block 4, how many physical blocks must be read from the disk? Answer

Answer 1

Solution:

suppose z is the starting file address

NOw,

Contiguous:

In this strategy: Divide the logical address by 512 and after it let's say D is the dividend and R is the remainder

D+z will be the physical block number. and the remainder R is the displacement into the block.

Linked:

In this strategy: Divide the logical address by 511 and after it let's say D is the dividend and R is the remainder

D+1 is the physical block number in the list, and R+1 is the displacement.

Indexed:

In this strategy: Divide the logical address by 512 and after it let's say D is the dividend and R is the remainder

The physical block address is indexed at D, and in the block.t, and R+1 is the displacement.

2)

I f we are currently at logical block 10 and want to access logical block 4, for that number of physical blocks must be read from the disk is :

Linked, the number of physical blocks must be read from the disk is 4.

Contiguous, the number of physical blocks must be read from the disk is 1.

Indexed, the number of physical blocks must be read from the disk is 2.

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