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The inode pointer structure not only allows for files to easily be allocated to non-contiguous blocks, it also allows the data at a particular location inside a file to be easily located. This is possible because the logical block size is fixed. For example, if each block is 8 kB, file data at 112 kB
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Unlike inodes, which are fixed in number and allocated in a special part of the file system, the indirect blocks may be of any number and are allocated in the same part of the file system as data blocks. The number of pointers in the indirect blocks is dependent on the block size and size of block
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The structure is partially illustrated in the diagram accompanying this article. The structure allows for inodes to describe very large files in file systems with a fixed logical block size. Central to the mechanism is that blocks of addresses (also called
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In the past, the structure may have consisted of about twelve pointers, but most modern file systems use fifteen pointers. These pointers consist of (assuming 15 pointers in the inode):
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to 120 kB would be pointed to by the third pointer of the first indirect block (assuming twelve direct pointers in the inode pointer structure).
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pointers. Example: with a 512-byte block size, and 4-byte block pointers, each indirect block can consist of 128 (512 / 4) pointers.
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The levels of indirection indicate the number of pointer that must be followed before reaching actual file data.
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https://inst.eecs.berkeley.edu/~cs162/sp20/static/sections/section9-sol.pdf
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Hierarchy/layout for directing inodes in a Unix File System
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77:Learn how and when to remove this message
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109:(UFS) to list the addresses of a file's
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240:"A Fast File System for UNIX"
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