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From: ast@cs.vu.nl (Andy Tanenbaum)
Newsgroups: comp.os.minix
Subject: Disk address size in V2.0
Message-ID: <7855@star.cs.vu.nl>
Date: 8 Oct 90 13:46:36 GMT
Sender: news@cs.vu.nl
Organization: Fac. Wiskunde & Informatica, VU, Amsterdam
Lines: 18


I am trying to decide whether V2.0 should have 13 3-byte disk addresses
in the inode or 10 4-byte disk addresses.  The former allows files up to
10K to be "small,"  the latter puts the limit at 7K. However, 3-byte
disk addresses require messy conversion when reading in or writing out an
inode.  UNIX uses the former scheme.

In any event, I will allocate 3 of the inode slots for indirect blocks,
although I probably won't put in the triple indirect block code now.  It is
a real mess for the case where you need a triple indirect block and the
disk only has 3 blocks left, so you allocate the triple, double, and 
single indirect blocks, then fail trying to allocate a data block.

If people have any opinions on the subject of 3-byte vs. 4-byte disk
addresses on the disk, please post comments.  In all cases, the in-core
structure will hold 4-byte addresses for speed in using them.

Andy Tanenbaum (ast@cs.vu.nl)