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I have 2 questions concerning the node array used by this file system which have i nodes to save the files.

Each i-node consists of

  • a user ID (2 bytes)
  • three timestamps (4 bytes each)
  • protection bits (2 bytes)
  • a reference count (2 bytes)
  • a file type (2 bytes)
  • size (4 bytes)

In addition, node-i contains

  • 13 direct indexes
  • an index to a level 1 index table
  • an index to a level 2 index table
  • an index to a level 3 index table

The system also stores the first 436 bytes of each file on node-i.

So, the questions are:

  1. Let's assume that a sector of the disk has 512 bytes, and that any auxiliary index table occupies an entire sector, what is the maximum size of a file in this system?
  2. Is there any benefit to the first 436 bytes of the file being stored on node-i?
β.εηοιτ.βε
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Tomàs Llorenç Guarino Sabaté
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1 Answers1

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Storing the first bytes of the file in the inode speeds up reads for files that can entirely fit in the inode itself. This is called inlining.

Because you mentioned 4 bytes (32 bits) are reserved for the file size, I'd expect 2^32 - 1 to be the max amount of sectors in a file.

From man newfs in OpenBSD:

The maximum size of an FFS file system is 2,147,483,647 (2^31 - 1) of 512-byte blocks, slightly less than 1 TB. FFS2 file systems can be as large as 64 PB.

Ronald
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