From owner-freebsd-hackers@FreeBSD.ORG  Wed Jun  8 10:07:26 2005
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Date: Wed, 08 Jun 2005 12:06:09 +0200
From: Ivan Voras <ivoras@fer.hr>
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To: Scott Long <scottl@samsco.org>
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Cc: David Malone <dwmalone@maths.tcd.ie>, scottl@FreeBSD.org,
	hackers@FreeBSD.org, Pawel Jakub Dawidek <pjd@FreeBSD.org>, phk@FreeBSD.org
Subject: Re: Google SoC idea
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Scott Long wrote:

> An alternate SoC project that would be very useful is block-level 
> snapshots.  I'm not sure if I'll be able to retain the filesystem 
> snapshot functionality in UFS with journalling enabled, so moving to 
> doing the snapshots in the block layer would be a good way to make up 
> for this.  Beware that while the GEOM transform would be pretty 

One addenum that was introduced after I made the post to hackers@, but 
before sending a proposal to Google (PHK's idea, actually) is to 
implement a delayed-commit mode, in which journaled data will not be 
commited until requested.

This would allow something like block-level snapshots, but one-shot only 
(or at least one per journal).