How does a file system like FastFile work?

Question

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?

Answer 1

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.