Linked Index Allocation

Single level linked Index Allocation

In index allocation, the file size depends on the size of a disk block. To allow large files, we have to link several index blocks together. In linked index allocation,

• Small header giving the name of the file
• Set of the first 100 block addresses
• Pointer to another index block

For the larger files, the last entry of the index block is a pointer which points to another index block. This is also called as linked schema.

Advantage: It removes file size limitations

Disadvantage: Random Access becomes a bit harder

Multilevel Index Allocation

In Multilevel index allocation, we have various levels of indices. There are outer level index blocks which contain the pointers to the inner level index blocks and the inner level index blocks contain the pointers to the file data.

• The outer level index is used to find the inner level index.
• The inner level index is used to find the desired data block.

Advantage: Random Access becomes better and efficient.

Disadvantage: Access time for a file will be higher.