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From: Robert Watson <rwatson@freebsd.org>
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To: "Wilkinson,Alex" <Alex.Wilkinson@dsto.defence.gov.au>
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Subject: Re: HEADS UP: UFS2 now the default creation type on 5.0-CURRENT
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On Tue, 22 Apr 2003, Wilkinson,Alex wrote:

> Can you recommend any papers that explain the differences between UFS1
> and UFS2 ie the benefits ? 

I don't believe there's a specific paper at this point, although no doubt
there will be.  The upshots are:

o 64-bit pointers up the wazoo
o Layout and functional changes to help support variable-size blocks
  (extent-like allocation) 
o Extension of various flag fields
o Addition of per-inode extended attribute extent
o Lazy inode initialization (watch newfs(8) fly)

The motivating factor in the layout change was the need for better EA
support, and while we were at it we figured we'd do a bunch of other
useful things too.  UFS2 uses the same basic technologies as modern UFS1
(inodes, linear directory layout, soft updates, snapshotting, background
file system checking, etc) so it was a relatively low-risk change.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Network Associates Laboratories